The day before, prepare the white chocolate chantilly. Bring the cream and vanilla to the boil. Place chocolate in a bowl and pour the hot cream mixture over the top. Stir in the gelatine and set aside in the fridge overnight.
The next day, preheat the oven to 160°C. Lightly grease an 18cm-round tart pan.
Roll out the pastry until it is large enough to line the tart pan. Ease pastry into the pan, trimming excess. Place on a baking tray and chill for 15 minutes.
Meanwhile, to make the frangipane, mix together all the ingredients until smooth.
Spread mincemeat mixture over the base of the chilled tart case, then top with frangipane. Bake in the oven for 15-20 minutes until the pastry and frangipane is cooked and golden. Set aside to cool.
Whisk the white chocolate vanilla chantilly cream (being careful not to over-whisk), and spread evenly over the tart to level it off. Place in the fridge.
Place apricot conserve in a bowl with 3 tbs water. Microwave to soften and warm through, then pass the mixture through a fine sieve. Dip the cherries into the apricot mixture to glaze, then arrange on top of the tart, starting around the outside and moving in.
To make the fondant snowflakes, roll the fondant on a surface liberally dusted with icing sugar until about 1-2mm thick. Use snowflake cookie cutters to cut out some shapes, and place on top of the tart to serve.