Step 1: Prepare Your Baking Pan - Line a 9x9-inch baking pan with parchment paper for easy removal once set.
Step 2: Melt the Butter - In a medium saucepan over low heat, melt the unsalted butter and stir occasionally.
Step 3: Mix in Sugars and Peanut Butter - Add brown sugar and powdered sugar to the melted butter, then mix in peanut butter and vanilla extract until smooth.
Step 4: Add Salt and Pour into Pan - Stir in salt, then pour the mixture into the prepared baking pan and spread evenly.
Step 5: Add Chopped Peanuts - Sprinkle chopped peanuts on top and gently press them into the fudge.
Step 6: Chill and Set - Refrigerate for at least 2 hours until firm, then lift out using parchment paper.
Step 7: Cut and Serve - Cut the fudge into squares and serve or store in an airtight container.
