Place the semi-sweet chocolate chips in a heat-proof bowl. Add half of the sweetened condensed milk.

Microwave for approximately 30 seconds, then stir until smooth. If additional melting is required, heat in 10–15 second intervals, mixing well between each session to prevent overheating.

Transfer the chocolate mixture onto a 10×15-inch baking sheet lined with parchment or wax paper. Spread the mixture evenly.

Place another sheet of wax paper over the surface and use a rolling pin or glass to flatten and smooth the layer. Refrigerate for a minimum of 5 minutes to allow it to firm.

In a separate heat-proof bowl, combine the peanut butter chips with the remaining sweetened condensed milk.

Microwave using the same method as the chocolate mixture. Stir until fully melted and creamy.

Remove the chilled chocolate layer from the refrigerator and spread the peanut butter mixture evenly on top.

If desired, add toppings at this stage.

Place wax paper over the layered mixture and gently smooth it. Refrigerate for 15–30 minutes, or until firm enough to roll without cracking.

Beginning at the long edge of the baking sheet, carefully roll the layered fudge into a tight log, using the wax paper to guide the process.

Wrap the completed roll in the wax paper and refrigerate for 1–2 hours, or until sufficiently firm.

Once fully chilled, remove the wax paper and slice the roll into pinwheel rounds using a sharp knife. Serve immediately or store as desired.