Melt the butter in a saucepan over a medium heat, then set aside 1 tbsp in a small bowl. Pour the milk and vanilla into the pan and simmer until warmed through. Combine the flour, yeast, sugar and a pinch of salt in a large bowl. Pour the milk mixture into the bowl and mix with a wooden spoon until well combined. Tip out onto a work surface and knead for 5 mins until you have a smooth and elastic dough. Roll the dough into a tight ball, sit in a clean bowl and cover. Leave somewhere warm to prove for 2-3 hrs until doubled in size, or chill for up to 48 hrs.

Tip the dough out onto a floured surface and knock out any air bubbles. Roll it into a round pizza base about 40cm wide. Dust a large baking sheet with a little more flour and put the dough on top. Use the chocolate chips to create a ring around the outside of the pizza base, 1/2cm from the edge. Brush a little milk inside the chocolate chip ring, then fold over the outside edge to enclose the chocolate and create a stuffed crust, pressing down very firmly to stick the dough in place. Can be prepared up to 1 hr ahead and set aside to puff up.

Heat the oven to 220C/200C fan/gas 8. Brush the middle of the dough with the reserved melted butter and bake for 15 mins until golden. Remove from the oven and spread over the chocolate spread and scatter over the marshmallows, if using, and any other toppings you like. Return the pizza to the oven for 4-5 mins to warm through the topping. Let stand for a minute before slicing to serve.