Butter a fairly deep, round loose-bottomed pie tin (4 × 23 cm). Roll out the pastry and use it to line the tin, or simply mould it in with the fingers. Leave to rest in the fridge. Melt the chocolate in an ovenproof bowl in a very low oven (50°C) for 5 minutes. Don’t overheat!
Turn the oven up to 150°C/Gas 2 and bake the almonds until lightly toasted. Chop in a food processor until ground quite small, but they don’t need to be smooth. Turn the oven up to 180°C/Gas 4. Set half the almonds aside. Add the bread to the remaining half and process until well mixed. Zest the lemon and juice it (take out pips). Beat the egg whites with a pinch of salt until they form soft peaks. Into the melted white chocolate, beat the egg yolks, followed by the lemon juice and zest, and the almonds and breadcrumb mixture. Fold in the egg whites.
Take the pastry case out of the fridge and spread the bottom with apricot jam. Dot the cherries over that, then sprinkle over the remaining ground almonds. Cover with the batter and bake in the oven for 45 minutes, or until a knife inserted into the middle comes out clean and dry. Serve warm or cold.