Chocolate Peanut Butter Cookie Sandwiches

Name: Chocolate Peanut Butter Cookie Sandwiches
Prep time: 30 min
Cook time: 1 h 20 min
Total time: 1 h 20 min
Yield: 12 pieces
Ingredients: 210 g smooth peanut butter; 200 g soft dark brown sugar; 1 medium egg; 2 Tbsp cocoa powder; 1 tsp gluten-free baking powder; 1 tsp natural vanilla extract; 40 g unsalted butter; 25 g smooth peanut butter; 80 g icing sugar; ½ tsp vanilla extract; ½ tsp milk