Start with heating the milk and water in a pan.

In a bowl, take peanut butter and add warm milk and water mixture over it. Whisk the mixture until smooth. Set it aside.

Prepare a baking sheet pan by greasing it with butter or oil. You can also use parchment paper and grease it.

Preheat the oven at 375-degree F.

Cream together butter, brown sugar, and granulated sugar in a mixing bowl. You can use a stand mixer or handheld machine whiskers.

Add eggs one by one in the butter and whisk well until cooperated.

Add flour, salt, vanilla, baking soda, buttermilk, oil, and the peanut butter mixture. Gently whisk the mixture until smooth. Try not to overbeat the mixture.

Now pour the buttermilk into the batter and fold it gently until well combined.

Pour the cake mixture over the prepared sheet pan and bake the cake for 20 to 25 minutes. Poke a toothpick; if it comes out clean, then your cake is ready; otherwise, bake more for 5 minutes until done.

Once the cake is baked, let it cool at room temperature for 8 to 10 minutes.

Meanwhile, prepare the frosting by heating the milk to a gentle simmer.

Add the milk to the peanut butter and whisk until smooth.

In a separate bowl, cream the butter and add heavy cream and vanilla to it.

Add the peanut butter mixture to it and mix.

Gradually add confectionary sugar to the mixture and fold until the frosting is creamy.

Pour the frosting over the cake.

Serve with the garnish of chopped peanuts.