Preheat oven to 350°F and prepare a 13 x 18" jelly roll pan non-stick baking spray.

In a large bowl, whisk together melted butter, milk, sour cream and sugar.

Whisk in egg and vanilla extract, followed by the flour, cocoa powder, baking soda and salt.

Pour the cake batter into your prepared jelly roll pan and bake for 20 minutes, or until a toothpick inserted in the center comes out clean.

Allow cake to cool for at least 10 minutes or so.

Cream peanut butter and regular butter in a stand mixer. Add vanilla and salt and continue mixing.

Gradually add powdered sugar, one half cup at a time, while mixing on medium speed. Scrape down the side of the bowl as needed to make sure everything is well incorporated.

When all sugar has been mixed in, the icing will appear dry — and that's ok! Add milk, one teaspoon at a time, and beat at medium speed until light and fluffy.

Spread one thick and even layer of peanut butter fudge on the top of the chocolate cake.

Combine butter, milk, corn syrup, and vanilla extract in small saucepan over medium heat. Cook until butter is melted, stirring occasionally. Reduce heat to low, add the chocolate, and whisk constantly until melted.

Remove pan from heat, add the powdered sugar, and whisk until smooth. Let the chocolate glaze sit for 5 minutes until it begins to cool and thicken.

Slowly pour glaze on top of the peanut butter fudge layer and use a spatula to gently spread the frosting towards the edges. Allow chocolate glaze  to harden – for about 30 minutes.