Preheat the oven to 200'C (gas mark 6-7).
Mix the butter, flour, sugar and ground almonds by hand until roughly combined. Spread this mixture onto a baking sheet lined with parchment paper.
Bake for approximately 15 minutes, then cool.
Combine the water and brown sugar, then bake at 120'C (check the temperature using a cooking thermometer). Place the egg yolks into a mixing bowl and whisk, gradually incorporating the hot syrup in small drizzles. Continue to whisk until completely cooled.
Mix the Grand Marnier to the sabayon, then carefully mix in the cream.
Put a layer of crumble into individual moulds or stainless steel rings. Pour in the cream and place in the freezer for 4 hours.
Just before serving unmould onto individual plates.
«You can also decorate the parfait with some toasted almonds. »