For the Chocolate Sheet Cake:

2 cups granulated sugar
2 cups all-purpose Gold Medal flour
1 teaspoon baking soda
1/2 teaspoon salt
2 large eggs, lightly beaten
1/2 cup buttermilk
1 teaspoon pure vanilla extract
1 cup unsalted butter
1/4 cup cocoa powder
1 cup hot water

For the Peanut Butter Frosting:

3 cups sifted powdered sugar
1/2 cup milk
1/2 cup creamy peanut butter
1 teaspoon vanilla extract

Reese's Peanut Butter Cups, chopped-optional