I'll outline the simple version and then provide details of the more complicated options.
- Chocolate muffin
- Chocolate sauce - the kind that goes on ice cream
- Strawberry or raspberry sauce - the kind that goes on ice cream
- Icing sugar
- Chop the muffin top off the top of your muffin.
- Upturn the main body of the muffin and crumble the top you've chopped off around the base of your forming volcano.
- Pour or squeeze chocolate sauce over your volcano (this is the cooled lava flow)
- Pour or squeeze strawberry/raspberry sauce over chocolate sauce (this is the hot lava flow)
- Sprinkle with icing sugar (snow atop your volcano)
- Admire and devour
- Make the muffins. I have a couple of recipe suggestions, here and here.
- Make a chocolate sauce. I found a bar of chocolate containing honeycomb pieces and chucked that in the microwave gently, until it melted. I figured the honeycomb would add an interesting texture. It was more spoonable than pourable but a cooled lava flow moves more slowly so it was quite authentic.
- Make a compote. This sounds posher than it was. I found a few left over raspberries, red currants and blackcurrants in the freezer and heated with a bit of water and neat blackcurrant squash. I then blended the resultant goo. The great thing about using this whilst warm is that when you sprinkle on your icing sugar at the end, it will dissolve on the compote in the same way that snow would not settle on hot lava.