Pan de huevo is “egg bread,” a popular item in Mexican bakeries that is also called “conchas.” The shell-shaped pastry is lightly sweetened on top with chocolate, vanilla, or strawberry sugar
 
“Pan de huevo” is cited in English from the 1850s and has been sold in San Antonio bakeries since at least the 1940s. Pan de huevo can now be found in many Texas supermarkets.
     
 
Borderlands - El Paso Community College
Tempting Sweet Breads : Pan de Dulce
By Lynn Cordova, Inez Caldwell, Victor Canchola and Florence Brame comps.
(...)
Pan de huevo (egg bread) refers to a number of different round flat breads with colored powdered sugar toppings and various flavorings. They are usually not very sweet except for the topping and taste great dunked in coffee. The powdered sugars form spiral and diamond shapes on the top of the bread, which is available in vanilla and chocolate. 
     
Hispanic.com
MMMmmm…Pan de Huevo
Pan de Huevo (sometimes called conchas) is a type of pan dulce which refers to small, brioche like golden breads covered with powdered sugar toppings which traditionally include chocolate, vanilla, and strawberry.
 
The sugars form designs on top of the bread which are individually created by each bakery.
 
According to The Austin Chronicle, pan dulce first became popular in Mexico when the French briefly attempted to colonize Mexico several centuries ago.  French influence spread to creating various pastries, albeit with a Mexican twist.  Porfirio Diaz in the early 1900s further tried to “modernize” and make Mexico and Mexican people more sophisticated by promoting European ideas/foods etc. and distaining traditional Mexican foods, traditions, cultures.
 
If you’ve got a hankering for some pan de huevo: we’ve pulled up a recipe for pan dulce from the San Antonio Cookbook. (...)
 
Mi Tierra Restaurant & Bakery (San Antonio, TX)
Pan de Huevo - White
“egg bread” It’s dense, rich, yeasty and not too sweet, topped with sugar.
Pan de Huevo - Chocolate
Chocolate-flavored sugar topping.
Pan de Huevo - Yellow
Vanilla-flavored sugar topping.
Pan de Huevo- Coco
Something a little different, a topping of toasty, sweet coconut.
     
Google Books
Travels on the Western Slope of the Mexican Cordillera
by Cincinnatus (Marvin Wheat)
San Francisco, CA: Whitton, Towne & Co.
1857
Pg. 134:
Some of their cookery consist of the following; Tortilla, pan de huevos, ensalada de tortilla, ensalada de carne, arroz de carne, quesadillas, sopa de pan, ensalada de piscada de tierra, and pan de trigo.
     
Google Books
Good Words for 1873
edited by Rev. Donald MacLeod
London: W. Isbister & Co.
1873
Pg. 454 (“Spring in Mexico,” edited by Canon Kingsley):
First of all, and best of all, was the chocolate brought to us soon after we landed by a barefooted Mexican boy, with “pan de huevos” (literally, “egg bread”), a sweet light cake.
 
Google Books
Appletons’ Guide to Mexico:
Including a chapter on Guatemala, and an English-Mexican Vocabulary
by Alfred R. Conkling
second edition, revised
New York, NY: D. Appleton and Company
1884
Pg. 52:
Pan de huevos, “egg” bread.
 
Google Books
Terry’s Mexico: Handbook for Travellers
by T. Philip Terry
second edition, revised
London: Gay and Hancock, Ltd.
1911
Pg. 470:
The white roll shaped something like a rosette, is known as pan de huevo (egg bread).
     
Google Books
Southwestern Lore
compiled by J. Frank Dobie
published for the Texas Folk-lore Society
Dallas, TX: The Southwest Press
1931
Pg. 69:
... or pan de huevo, or the frijoles the Mexicans cook so well.
   
12 November 1949, San Antonio (TX) Light, pg. 2, col. 1:
Jose Bernal Moreno has been baking pan de dulce in San Antonio for 53 years.
 
He came here shortly before the turn of the century, after learning the art of pastry making in Monterrey. he recalls:
 
‘There were times when I went out and cut mesquite wood for my oven.”
 
Moreno is a good hand at all varieties of pan de dulce, among them pan de huevos (egg buns) and the rock-shaped pan de piedras.
 
18 April 1952, Park Forest Star (Chicago, IL), pg. 2, col. 2:
Mexican bakeries (In Los Angeles—ed.) aren’t as numerous as delicatessens like Pedro’s, but it’s a real experience to go into one. Even if your Spanish is strictly of the book variety you can usually find someone to tell you what the names of the various pastries mean. “Pan dulce,” which means “sweet bread,” are what the bakeries specialize in since tortilla factories make what Mexicans use for bread.
 
Going up to the shelves where the pan dulce is placed in trays is like going up to the penny candy case in an old-fashioned store. To choose from are “pan de huevo” or egg bread, “Elotitos” or cobs of corn, “cuernos” or horns, “abrazos” or hugs, “besos” or kisses. Untranslatable items are such things as “chamucos” and “campechanas.” There is also a delicate leaf pastry filled with custard which has various names, one of which is “pastelitos de hoja,” which translated liberally means “little pies of leaves.”
   
14 July 1960, San Antonio (TX) Light, pg. 48 ad:
Pan De Huevo
EXTRA RICH IN EGGS
Doz. 49c
 
19 February 1961, Deming (NM) Headlight, pg. 12, col. 1:
It sure has an exquisite flavor, especially accompanied by Italian spiced cake, this is a recommended good starter for cold mornings, of course it is no substitute for the famous Mexican Pan de huevo (sweet bread) with frothy hot chocolate.
 
22 July 1964, Oakland (CA) Tribune, pg. 6X, cols. 3-6:
PAN DE HUEVO CHILENO
(Chilean Egg Rolls)
One cup milk
One-quarter cup sugar
One-half teaspoon salt
One-third cup warm water (105 to 115 degrees F.)
One package of cake yeast, active dry or compressed
Four and three-quarter cups unsifted flour, about
One-half cup water
One-half teaspoon anise seed
Two egg yolks, slightly beaten
One-quarter cup (one-half stick) margarine, melted. (...)
 
4 May 1968, Victoria (TX) Advocate, pg. 5, col. 3:
SAN ANTONIO (AP)—Some 6,700 school-aged children invaded the 92.6 acre grounds of San Antonio’s HemisFair Friday.
(...)
Sunday a ceremony featuring the breaking of “pan de huevo” (Mexican egg bread) will mark a joint observance of San Antonio’s 250th birthday anniversary and Cinco de Mayo—Mexico’s independence from France.
 
9 April 1970, Galveston (TX) Daily News, pg. 14A, col. 3 ad:
SOMETHING NEW AT G&G BAKERY
MEXICAN PASTRIES
 
ECHO POR JOSE HUERTA
PAN DE HUEVO MEXICANO
NOVIAS - POLCAS - CONCHAS
REVENTONES - ARMADILLOS
CAMPECHANAS - MANITAS
EMPANADAS - PASTEL DE POLVO
CAFE CAKE MEXICANO
SEMITAS DE CANELA
HERRADURAS
   
24 December 1970, San Antonio Express, pg. 27C, col. 4 ad:
La Providencia Bakery
Specializing in Pan de Huevo
 
19 May 1971, Arizona Daily Sun (Flagstaff, AZ), pg. 2, col. 7 ad:
NOW FEATURING…MEXICAN PASTRIES
. CONCHAS
. PAN DE HUEVO
PERPETUAL BAKERY
 
7 July 1977, San Antonio (TX) Light, “Pan Dulce: S.A. Has the Best” by Ed Castillo, pg. 2B, col. 3:
Mi Tierra alone baked more than 30 varieties of the sweet bread which is so eagerly sought by local residents from all quadrants of the city.
 
Some of the more popular pieces of pan dulce are the “pan de huevo” (egg bread); “polvoron” (comes from the word “polvo,” or dust, which is the fine sugar sprinkled over it); “empanada” (Pg. 3B, col. 3—ed.) (turnover, usually filled with sweet potato, apple or pineapple); “Ricardos” (named after the head baker, bread topped with glazed sugar and nuts).
 
Others: “Florecita” (little flower); “piedra” (rock); “cuerno” (horn); “caracol” (snail); “concha” (shell); “perla” (pearl); “chilindrinas” (the bright ones), and “semita de anis” (anise bun). There are many others.
         
MySA.com
A glossary of popular pan dulce (June 9, 1999)
Hector Saldana   San Antonio Express-News
Food Page 1F (356 Words)
   
Campechana - flaky, layered pastry with sugary glaze
Empanada - fruit-filled turnover, usually with pumpkin filling
Marranito - little brown piglet-shaped molasses cookie
Pan de huevo - slightly sweet, dense yeast-dough bread flavored with vanilla and stick cinnamon. Often called conchas for its shell pattern
Cuernito - sugary, cinnamon horn of pan de huevo
Piedra - cookie made from day-old bread with pink icing
Oreja de wey - rolled French pastry shaped… 
 
Austin (TX) American-Statesman blogs
A Love Affair with Pan Dulce
Posted 11.14.2006 4:59:17 AM
(...)
Most Mexican pastries are not very sweet.  Pan de huevo is a lightly sweetened bread topped with colored sugar.