Chop the Mars bars into small pieces. This will make them easier to melt.

In a saucepan, add the butter and the chopped Mars bars and melt slowly on low heat.

Stir the mixture continuously until the Mars bars have completely melted and combined with the butter. Be sure to keep the heat low to prevent burning.

In a large mixing bowl, pour the melted Mars bar and butter mixture over the rice krispies. Use a spatula to gently fold the mixture until all the rice krispies are evenly coated.

Prepare a baking tray by lining it with parchment paper or greasing it lightly with butter. Transfer the Mars bar and Rice Krispie mixture to the baking tray, then use the back of a spoon or spatula to press it down evenly into the tray. (Honestly, this recipe has so much butter that even if you don't line the tray with parchment paper, you are probably still safe!)

In a separate bowl, melt the cooking chocolate in the microwave or using a double boiler until smooth and creamy. If melting in the microwave, make sure to melt in small increments, e.g., 30 seconds at a time, stirring between each. Chocolate can burn very quickly in the microwave, and there is no saving it if this happens.

Pour the melted chocolate over the Mars bar and Rice Krispie mixture, spreading it evenly with a spatula.

If desired, sprinkle your choice of decorations over the melted chocolate. This could include chopped nuts, smarties, sprinkles, or even additional pieces of chopped Mars bar for extra indulgence.

Place the baking tray in the refrigerator and allow the Mars Bar Munchies to set for at least 1-2 hours or until the chocolate is firm.

Once set, remove the tray from the refrigerator and use a sharp knife to cut the Mars Bar Munchies into squares or bars. To make cutting easier, dip the knife into a mug of hot water between each slice. This technique helps prevent the mixture from sticking to the knife, ensuring clean and uniform cuts.

Serve and enjoy!