1. Crush the biscuits to coarse crumbs in a food processor (or alternatively pop then into a plastic bag and bash with a rolling pin). Mix the biscuit crumbs with the melted butter and press into the base of a 20cm loose-bottomed cake tin in an even layer. Refrigerate for about 10 minutes, until firm.

2. Pour the condensed milk and cream into a large bowl. Finely grate the zest from 2 of the lemons and add to the bowl. Squeeze the juice from the remaining lemons and add this into the mixture. Stir, until everything is well incorporated; the mixture will become very glossy, thick and smooth.

3. Spoon the lemon mixture over the biscuit base and refrigerate for 2 hours or so, until firm. Carefully remove the flan from the tin and arrange the raspberries over the top. Dust with icing sugar and serve in slices.