Texas Sheet Cakes are usually served right from the pan it's baked in. And they tend to serve a large number of people, so they're great to potluck parties. The size of the baking pan is important. Texas Sheet Cakes are supposed to be flat and are baked in a large (usually 10x15-inch) jelly roll pan. So avoid trying to bake it in a smaller cake pan, hoping for a taller cake; it won't turn out well.
Preheat oven to 375°F (190°C). Grease a 10x15x1-inch baking sheet (or jelly roll pan).
In a large saucepan, bring 1 cup butter or margarine and water to a boil. Remove from heat, and stir in flour, sugar, eggs, sour cream, 1 teaspoon almond extract, salt, and baking soda until smooth. Pour batter into a greased 10 x 15 x 1 inch baking pan.
Bake in preheated oven for 20 to 22 minutes, or until cake is golden brown and tests done. Cool for 20 minutes.
Combine 1/2 cup butter or margarine and milk in a saucepan; bring to a boil. Remove from heat. Mix in sugar and 1/2 teaspoon almond extract. Stir in nuts. Spread frosting over warm cake.