Chocolate peanut butter icebox cake

Ingredients

• 1/4 cup Dutch-process cocoa powder
• 1/4 cup black cocoa powder
• 1/4 cup creamy peanut butter
• 1/2 cup unsalted butter (cold)
• 1 1/4 cups sugar
• 1 egg
• 1 3/4 tsp vanilla extract
• 1/2 tsp baking powder
• 1/2 tsp salt
• 1 1/2 cups flour
• 1 1/2 cups heavy cream (cold)
• salt
• chocolate shavings (for garnish)