Step 1

Line an 8-by-8-inch baking pan with parchment paper, leaving a 2-inch overhang on all sides. Grease the paper with nonstick cooking spray. Set aside.

Step 2

Combine the sugar, milk, and salt in a medium saucepan. Bring to a boil, stirring constantly, over medium heat. Cook, stirring constantly, until mixture registers 230° on a candy thermometer, 2 to 2 1/2 minutes. Remove from the heat and quickly stir in the peanut butter and vanilla extract until smooth.

Step 3

Immediately pour the peanut butter mixture into the prepared pan and spread into an even layer. Let the fudge cool completely at room temperature until the bars are set, about 2 hours.

Step 4

Using the parchment paper handles, lift to remove the fudge from the pan. Cut the fudge into 16 squares.

Step 5

Place chocolate chips in a small microwave-safe bowl. Microwave in 30-second intervals, stirring in between each, until the chocolate is almost smooth with some unmelted bits remaining. Remove the chocolate from the microwave. Stir until the residual heat fully melts the chocolate and the mixture is smooth (microwave an additional 15 seconds, if needed). Drizzle the fudge with melted chocolate and sprinkle with the peanuts. Let stand until chocolate is hardened, about 20 minutes.