Prepare the Pan:

Line an 8×8-inch square baking pan with parchment paper or foil, leaving an overhang on the sides for easy removal. Lightly grease it if using foil.

Melt the Chocolate Layer:

In a saucepan over low heat (or using a microwave-safe bowl in 30-second bursts), combine the chocolate chips and half of the sweetened condensed milk (about 2/3 cup). Stir until melted and smooth. Add a pinch of salt if desired.

Layer the Chocolate Base:

Pour half of the chocolate mixture into the prepared pan and spread evenly. Place the pan in the refrigerator or freezer for about 10 minutes to firm up slightly.

Make the Peanut Butter Layer:

In a clean saucepan or bowl, combine the peanut butter and the remaining sweetened condensed milk. Stir over low heat or microwave until smooth and creamy.

Add the Peanut Butter Layer:

Pour the peanut butter mixture over the chilled chocolate layer and spread evenly.

Top with Remaining Chocolate:

Reheat the remaining chocolate mixture if needed to loosen it up. Pour it over the peanut butter layer and spread evenly. Sprinkle roasted peanuts on top if using.

Chill to Set:

Refrigerate the fudge for at least 2 hours or until firm.

Slice and Serve:

Lift the fudge out of the pan using the parchment or foil overhang. Cut into squares and enjoy! Store in an airtight container in the refrigerator for up to one week.