Beat the egg yolks with the sugar until thick and light. Melt the butter and chocolate over hot water until smooth. Cool slightly. Add the liqueur to the egg yolks and gently fold in the cooled chocolate. Fold in the ground almonds.

Whisk the egg whites until stiff peaks form. Fold a few Tbls. Of the whites into the chocolate mixture to lighten it. Fold the remaining egg whites into the chocolate mixture gently. Pour into a greased and lined 20cm (8in) deep cake tin and bake at 180 °C/350F until done but still a bit runny in the centre...as you would for brownies. This could take anywhere between 40, 60 minutes. It's best to test it after 40 minutes and keep an eye on it from then on. Remove from the oven and allow to cool in the tin for 10 minutes and then let cool on a wire rack.

This cake is nice served with berries and creme fraiche or heavy cream. It is also lovely covered with rich ganache glaze made with equal parts of heavy cream and dark chocolate...add a Tbls. Of the same liqueur you used in the cake....and swirl it over the cake.