2. In a microwave-safe bowl, melt the marshmallows and butter in 30 second bursts, stirrying after each burst. This will take 2-3 times. Alternatively you can do this in a saucepan over low heat.

3. Place the rice bubbles into a large bowl, and combine with the marshmallow mixture. Stir to combine. This is going to be sticky and messy, go with it.

4. Pour the mixture into the prepared tin, and press in to the edges, Using the back of a spoon, smooth over the top of the slice. Sprinkle with decorations.

5. Refrigerate for 1-2 hours, and then remove and cut into squares. Store in an airtight container.