In a large mixing bowl, add marshmallows, milk chocolate morsels, semi sweet chocolate morsels, and baking chocolate. Set aside.
In a large pot over medium-high heat, combine granulated sugar, milk, and 1 cup butter. Stir constantly and bring to a boil. Boil for 2 minutes. Remove from heat and stir in vanilla extract. Pour hot mixture over marshmallows and chocolates.
Using an electric mixer with a whisk attachment, beat the mixture until smooth and melted, which may take several minutes.
Pour the chocolate mixture into a parchment paper-lined 15x10x1 inch baking sheet.
In a small saucepan over medium heat, warm the sweetened condensed milk and 2 tablespoons butter until butter is melted. Add peanut butter morsels and whisk until smooth. Remove from heat.
Pour the peanut butter mixture over the chocolate layer and swirl top with a knife. Allow the fudge to set for 2 hours. Cut into pieces and enjoy!
Notes
This fudge is perfect for holiday gifts or any sweet occasion. Store leftovers in an airtight container.