Preheat the oven to 350°F (180°C).
Tear the croissants into pieces and put them in a medium oven safe casserole.
Mix together the cream, milk and liquor and set aside.
Stir the sugar and water together in a saucepan until the sugar is just dissolved.
Place the saucepan on a burner over medium high heat.
Let the sugar and water caramelise by leaving it to bubble away on the stove without stirring for about 3 to 5 minutes. Keep a close eye on it, and when it turns a deep amber colour, the caramel is ready.
Turn the heat down to low and add the cream, milk and liquor mixture, whisking constantly.
Once all the caramel has dissolved into the cream, remove the pan from the heat.
Whisk in the beaten eggs.
Pour the caramel custard over the croissants in the casserole. Leave to sit for ten minutes before baking.
Bake for 20 minutes or until golden brown.