Grease a 25 cm loose-bottomed cake tin with butter and line the base with nonstick baking paper.

Melt the butter and chocolate in a heatproof bowl set over a pan of gently simmering water, making sure the bottom of the bowl does not touch the water.

Remove from the heat, stir in the Amaretto and leave to cool.

Whisk the egg yolks and sugar in a bowl until pale and thick.

Fold into the chocolate mixture with the ground hazelnuts.

Whisk the egg whites in a separate clean bowl until soft peaks form, then carefully fold 2 tablespoons of the mixture into the chocolate mixture.

Repeat until all the whites are folded in.

Spoon the mixture into the prepared tin and level the top.

Arrange the pear halves over the mixture, cut side down.

Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 40 minutes until the pears are soft and the cake is cooked through.

Leave to cool slightly in the tin, then turn out on to a wire rack and leave to cool completely.

Dust with icing sugar and serve with low-fat crème fraîche, if liked.