Cake:

1. Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan.
2. In a large bowl, combine flour, sugar, and baking soda.
3. In a saucepan, bring water, butter, vegetable oil, and peanut butter to a boil. Pour over the flour mixture and mix well.
4. Add milk, eggs, and vanilla extract. Mix until smooth.
5. Pour batter into the prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
6. Let the cake cool completely before icing.

Icing:

1. In a medium saucepan, combine butter, peanut butter, and milk. Heat until the butter and peanut butter are melted and smooth.
2. Remove from heat and stir in vanilla extract.
3. Gradually add confectioners’ sugar, beating until smooth and creamy.
4. Spread the icing over the cooled cake.