Preheat the oven to 180°C (160°C fan). While it's heating, place the digestive biscuits into a sturdy resealable bag and crush them using a rolling pin until you have a mix of fine crumbs and small pea-sized pieces. You should hear a satisfying crackling sound as the biscuits break down, and the crumbs will smell warm and malty.

Combine the crumbs with melted butter. Pour the melted butter into a medium bowl, tip in the biscuit crumbs, and stir with a fork until every crumb looks damp and darkens slightly in colour. The mixture should hold together when you press it between your fingers, like wet sand at the beach.

Divide the crumb mixture evenly between your four ramekins. Press it down firmly using the back of a spoon or the bottom of a small glass. You want a compact, even layer that reaches about halfway up each bowl. The surface should feel solid and smooth to the touch, with no loose crumbs rattling around.

Make the chocolate ganache layer. Place the chopped dark chocolate in a heatproof bowl. Heat the double cream in a small saucepan over a medium heat until small bubbles appear around the edges and steam begins to rise steadily. Pour the hot cream over the chocolate and let it sit undisturbed for one minute. Then stir gently in one direction until the mixture becomes glossy, thick, and completely smooth. It will look like a dark, satiny river and smell intensely of rich cocoa.

Stir in the vanilla extract and a pinch of sea salt. The salt will cut through the sweetness and make the chocolate taste deeper. Spoon this ganache evenly over the biscuit bases in each ramekin, spreading it to the edges. The layer should be about 1cm thick and will look dark and shiny.

Scatter the milk chocolate chips over the ganache, if using. This creates little pockets of extra melty chocolate as it bakes. Then top each bowl with a generous handful of pork-free marshmallows. Arrange them so they cover the surface, but leave tiny gaps so you can see the chocolate beneath. The marshmallows should look pale, puffy, and slightly springy.

Bake for 12-15 minutes. Place the ramekins on a baking tray to catch any drips. Bake until the marshmallows are puffed up, golden brown on top, and just starting to collapse slightly at the edges. You'll hear a faint sizzling sound from the bubbling chocolate underneath. The tops should be a warm honey colour, not dark brown. If you prefer a deeper toast, you can finish them under the grill for 30 seconds, but watch them like a hawk — they burn in an instant.

Let them rest for 3-4 minutes before serving. This is crucial. The bowls will be volcanic straight from the oven. During this short rest, the chocolate sets slightly and the marshmallows settle into a soft, pillowy layer. The bowls should still be warm to the touch when you serve them, but not dangerously hot.