To prepare the lava cakes, generously grease the pans or ramekins with the 3 tbsp (1¾ oz./50 g) butter. Coat the bases and sides with sliced almonds. Chill on the baking sheet until using.
Sift the flour and baking powder into a bowl.
Melt the chocolate in a bowl over a saucepan of barely simmering water (bain-marie) until the tem