The office is having a going-away party tomorrow. The honoree decided he wanted a potluck lunch, which means I will be able to eat at least one thing there--the dessert, because I am bringing it. Potlucks mean either Cherry Cobbler (see here) or Texas Sheet cake because they are both made in a jelly-roll pan and serve a lot.
There are recipes for this all over the web. Some leave out the word "Texas". Epicurious calls it a Chocolate-Buttermilk Sheet Cake. Some are baked in a 15x10" jellyroll pan and are thin. Some are baked in a 13x9" pan with the same amounts and they are thicker. They are all about the same. Here's mine:
Texas Sheet Cake
1 cup water
1/2 cup (1 stick) unsalted butter
1/2 cup plus
1/2 cup vegetable oil
1 tsp vanilla extract
1 teaspoon baking soda
2 cups sugar
2 cups all-purpose flour
1/2 teaspoon salt
1/2 cup buttermilk, yogurt, sour cream, or milk soured with a couple teaspoons of vinegar
2 large eggs
1/2 cup unsalted butter (1 stick)
3 Tbsp cocoa
1/4-1/3 cup milk (depends on whether whole milk, 2% or skim, and the weather)
1 tsp vanilla extract
1 pound powdered sugar (about 4 cups)
1/3 cup chopped pecans or walnuts
1/3 cup miniature semisweet chocolate chips (soy-free)
Preheat oven to 350°F. Butter a 15 1/2 x 10 1/2 x 1-inch jelly-roll pan. Put water, 1 stick butter, cocoa powder, vegetable oil, vanilla and baking soda in large microwave safe bowl. Microwave by 30-second intervals, stirring after each, until the butter is melted and the cocoa is mixed in. Whisk in sugar, flour, salt, then buttermilk (or equivalent) and eggs. Spread batter in prepared pan. Bake cake until a toothpick inserted into center comes out clean, about 20 minutes. Transfer cake in pan to a rack.
Meanwhile, melt remaining stick of butter in a medium saucepan over medium heat. Remove from heat. Stir in with a wooden spoon: powdered sugar, milk (start with 1/4 cup), the 3 tablespoons cocoa powder and 1 teaspoon vanilla. Add more milk if you need to to make the frosting spreadable--not so thick that it will rip up the top of the cake.
Spread frosting over warm cake. Sprinkle with nuts and mini chocolate chips. Press in slightly. Cool cake (and carry it to your party) in pan. Cut into 24 pieces.