Heat oven to 160C/fan 140C/gas 3. Chop the pears into small pieces and put in a pan with the lemon juice and sugar. Bring to the boil, then cover and cook for 10 mins. Uncover, then cook for 8-10 mins more until the juices thicken up. Spoon into 4 x 150ml ramekins and add a teaspoon of liqueur to each, if using.
For the topping, sift the icing sugar and cocoa into a bowl, then stir in the almonds. Whisk the egg white until stiff, then fold into the dry ingredients. Spoon over the pears and shake the ramekins to level the mixture.
Bake for 20-25 mins until the topping is firm to the touch. Serve warm or cold.