Try this Buckeye Brownies recipe
Allowing the baked base to cool completely before applying any dairy-based topping prevents the butter in the peanut butter cream from melting and oiling off. Beat the softened unsalted butter and creamy peanut butter on medium speed for a full two minutes to incorporate air, which yields a lighter texture that spreads easily. Adding the powdered sugar in half-cup increments prevents airborne clouds and ensures proper hydration without lumps. Whip the mixture for another one to two minutes after adding the vanilla extract, milk, and salt to guarantee homogeneity. Melt the semi-sweet chocolate and the remaining quarter-cup of peanut butter together over medium-low heat, stirring constantly to prevent scorching the milk solids in the chocolate. Cool this glaze for several minutes before pouring it over the buttercream layer to avoid thermal shock that causes the underlying fat to separate. Chill the assembled pan for exactly one hour to set the chocolate shell properly for clean slicing. Storing leftovers in an airtight container in the refrigerator for up to three days firms the peanut butter center into a dense, fudge-like consistency.