Preheat your oven to 350°F (175°C). Grease your 9x13-inch baking pan or line it with parchment paper for easy removal later.
In a double boiler or microwave, melt the 2 sticks of salted butter and 4 ounces of chopped milk chocolate together until smooth. Stir occasionally to prevent burning. Once melted, set aside to cool slightly.
In a large mixing bowl, combine the melted chocolate mixture with 1 1/2 cups of granulated sugar and 1 tablespoon of vanilla extract. Whisk until well blended. Add in the 4 large eggs, one at a time, mixing well after each addition.
Sift together 1 cup of unsweetened cocoa powder, 1 cup of all-purpose flour, and 1/4 teaspoon of kosher salt. Gradually fold this mixture into the wet ingredients until just combined. Be careful not to overmix!
Pour the brownie batter into the prepared baking pan, spreading it evenly. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Remove from the oven and let cool.
While the brownies are cooling, prepare the peanut butter layer. In a mixing bowl, beat together 1 cup of creamy peanut butter and 2 tablespoons of room temperature salted butter until smooth and creamy. Spread this mixture evenly over the cooled brownie layer.
In a small saucepan over low heat, combine 2-3 cups of semi-sweet chocolate chips until melted. Stir in 1 cup of Rice Krispies cereal until well coated. Pour this crunch topping over the peanut butter layer, spreading it out evenly.
Cover the pan with plastic wrap or foil and refrigerate for at least 2 hours to allow the layers to set properly. Once chilled, cut into squares and serve!