Line a 8x8 square baking dish with plastic wrap. Set aside.
In a heavy bottom saucepan, heat the 1/2 cup unsalted butter over medium heat.
When melted, stir in the 2 cups brown sugar and 1/2 cup whole milk, stirring to combine. Bring to a simmer. When you start to see bubbles, time about 3 minutes, stirring constantly. Mixture should be smooth. Do not overheat, it will seperate.
Remove from the heat and whisk in the 1 cup peanut butter and 1 teaspoon vanilla extract.
Pour the peanut butter mixture over the 3 cups powdered sugar in a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment. You will get the best results using an electric mixer versus hand mixing and pre-sifting your powdered sugar.
Mix until smooth, approximately 4 minutes.
Pour into the prepared square baking dish. Pat the 1/4 cup mini chocolate chips into the top of half of the fudge.
Cover with plastic wrap and refrigerate until firm, approximately 8 hours.
Cut and serve. I prefer to keep my fudge chilled until ready to serve.
If you've tried this recipe, come back and let us now how it was in the comments or star ratings.
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Notes
Adapted from AllRecipes. Storage: I like to keep my fudge chilled until ready to serve, rather than at room temperature. Be sure to store in an airtight container. Freezing: This easy recipe also freezes really well. Wrap tightly with plastic wrap then store in an airtight container for up to two months.