Preheat oven to Gas Mark 4, 180°C, 350°F. Cream butter and sugar together until light and fluffy. Gradually beat in eggs then fold in flour. Divide mixture between lightly greased bun tins (or silicone moulds). Bake for 12-15 minutes until just firm to the touch and golden.
Cool for 10 minutes then turn out of tins to cool completely.
Whip the crème fraîche until it just holds its shape then spread on to the base of one cake, spread jam on the other base and sandwich together. Dust with icing sugar.
Unfilled they will keep for up to three days, once filled they should be eaten the same day.
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