For the Brownies:

1. Prep: Preheat oven to 350°F. Grease an 8×8 metal pan generously with butter/cooking spray or line with parchment.
2. Melt Chocolate Mixture: In a microwave-safe bowl or glass measuring cup, melt the butter and chocolate chips together in short 10-20 second bursts until smooth, stirring frequently. Be careful not to let the mixture get too hot.
3. Wet Ingredients: In a medium mixing bowl, whisk together eggs and vanilla. Stream the slightly cooled butter and chocolate mixture into the eggs and vanilla while whisking. Whisk until smooth.
4. Combine with Dry: Add the brownie mix and combine using a hand mixer or a stand mixer with a paddle attachment until no flour is visible (but be careful not to over-mix). The batter will be thick.
5. Bake: Spread the batter into the prepared metal pan so that it is evenly distributed. Bake for 22-27 minutes, rotating halfway through the bake time. Insert a toothpick to check doneness. They’re done when there are only a few moist crumbs remaining on the toothpick and no wet batter is visible. Let brownies cool to room temperature.

For the Peanut Butter Frosting:

1. While the brownies are baking, microwave peanut butter and 4 tablespoons of butter together in a medium-sized heatproof bowl until the butter is fully melted and the mixture is smooth.
2. Add 1/2 teaspoon of vanilla, powdered sugar, and milk, and mix using a hand mixer or in a stand mixer on medium to low speed until no powdered sugar is visible. The mixture will be very thick and dough-like.
3. Cover and set aside. Once brownies are cool, press peanut butter mixture into an even layer on top of the brownies.

For the Ganache:

1.  Place 1 cup of chocolate chips in a medium-small bowl and set aside.
2. In a small pot, heat the heavy cream over low to medium heat until it is hot and steam is visible. (Note: Small bubbles on the edge of the pot are okay but watch carefully so that the cream does not boil).
3. Pour cream over the chocolate chips and let sit 3-4 minutes, then whisk together until smooth. Pour over the peanut butter layer on the brownies and spread until smooth, tapping the pan on the counter a couple times to pop any air bubbles.
4. Let chill in the refrigerator for 30-60 minutes until firm before slicing. Store in the fridge for best results, but they can be served either chilled or at room temperature for up to 5 days.

Freeze For Later: Freeze in an airtight container or freezer-safe bag after they are fully cooled. The brownies can be frozen before or after they are sliced and kept in the freezer for up to 3 months.

Prepare From Frozen: When you’re ready to enjoy them, thaw in the fridge or microwave them in 5 second intervals.