Place the whole dates in a bowl and sprinkle the liqueur over. Leave for 4 hours, then strain, reserving the liqueur. Halve the dates and remove stones.
Make the base:
Preheat the oven to 180 degrees C. Grease and line a 22cm springform pan.
Place all the dry ingredients in a food processor and pulse to mix. Add the butter and egg and pulse until coarse crumbs form. Press into the base of the tin and chill for 30 minutes. Bake 25 minutes until golden.
Make the filling:
Combine the mascarpone, cream cheese and sugar in the food processor until creamy. Add the eggs, lemon juice and zest and reserved liqueur and mix until combined.
Arrange the dates over the cooked base and pour over the mascarpone mixture. Bake at 160 degrees C for 1 hour. Cool in oven with the oven door open. Chill for four hours.