Step 1

Preheat the oven to 350 degrees Fahrenheit. Prepare a rimmed baking sheet by greasing it with butter.

Step 2

Using a large bowl and whisk, combine the flour, sugar, and baking soda. Then, mix in the milk, eggs, and vanilla with a hand mixer. (Low speed) Mix until smooth.

Step 3

Add the water, butter, oil, and peanut butter to a saucepan. Cook over medium heat, stirring regularly, for approximately 5 minutes. Once the mixture is smooth, add it to the flour mixture. Combine.

Step 4

Pour the batter mixture into the greased baking sheet. Spread evenly.

Step 5

Bake at 350 degrees in the preheated oven for approximately 20 minutes. Then, remove the cake from heat, and use the toothpick test to ensure it's done.

Step 6

Using a clean saucepan, melt the butter and peanut butter over medium heat, stirring frequently. Once the mixture is smooth, add the milk and vanilla. Stir until combined.

Step 7

Add the confectioner's sugar. Using a whisk, whisk for approximately 3 to 5 minutes. The icing should be uniformly smooth when it's ready.

Step 8

Remove the icing from the heat and pour it over the cake while it’s still warm. Then slice, serve, and enjoy!