-
1
Place the stoned dates in a bowl. Pour the boiling water over them, add the bicarbonate of soda, and leave to soak for 10–15 minutes. Transfer to a blender or food processor and process to a completely smooth paste. The paste must show no visible pieces of date; any remaining chunks at this stage will be detectable in the finished sponge.
-
2
Heat the oven to 180 °C. Beat the softened butter and brown sugar together until the mixture is pale and the sugar is substantially dissolved. Add the eggs one at a time, beating well after each addition. Fold in the sifted flour, then fold in the date paste. The batter will be looser than a standard sponge batter; this is expected.
-
3
Butter a 20 cm square baking tin or individual dariole moulds. Pour in the batter and bake for 25–30 minutes, until the sponge is just set at the centre — a skewer inserted into the middle should emerge with only the faintest trace of moist crumb. Do not overbake; a dry sponge cannot be recovered.
-
4
While the sponge bakes, make the toffee sauce. Combine the dark brown sugar, butter, double cream, and espresso in a heavy saucepan over a medium heat. Stir continuously until the butter melts and the sugar dissolves completely, then allow the sauce to bubble for 3–4 minutes until it thickens to a consistency that coats the back of a spoon. The sauce is ready when it smells of deep caramel rather than raw sugar.
-
5
This is where the dish lives or dies. With 5 minutes of baking time remaining, remove the sponge from the oven, pour a generous layer of hot toffee sauce directly over the surface, and return it to the oven for the final 5 minutes. The baked-in sauce caramelises against the sponge's surface, producing a depth of flavour that no amount of sauce added only at service can replicate. The surface should emerge from the oven glossy, bubbling at the edges, and darkened to a deep amber.
-
6
Turn the sponge out, or serve directly from the tin in generous squares. Ladle a substantial pool of the remaining hot toffee sauce around and over each portion — the sauce must be poured hot so that it penetrates the warm sponge rather than congealing at the surface. Serve immediately with clotted cream or vanilla ice cream alongside.