For the crêpes, mix the flour and eggs together in a bowl until well combined. Add the milk, whisking all the time, until the batter is smooth and the consistency of double cream, adding more milk as necessary. Stir in half of the melted butter.
Heat the remaining butter and the oil in a frying pan and pour in a ladleful of the crêpe batter and swirl the pan around to coat the surface. Fry for 1-2 minutes, then flip over and fry for a further 1-2 minutes, or until golden-brown all over. Repeat with the remaining batter.
For the banana, roll the banana chunks in the crushed biscuits. Melt the butter in a frying pan, add the banana pieces, sprinkle over the brown sugar and fry for 2-3 minutes, or until the bananas are golden-brown.
To serve, place half of the chocolate into a bowl set over a pan of simmering water. (Do not allow the base of the bowl to touch the water.) Stir until melted.
Place the crêpes onto a serving plate, scatter over the banana pieces and spoon the ice cream on top. Scatter over the remaining chocolate and fold the crêpe over twice to form a triangle. Drizzle the melted chocolate over the top and sprinkle over the raspberries.