Preheat the oven to 200C/400F/Gas 6.
Roll the block of pastry to 3-4mm thick, and lay over a 20cm/8in fluted tart tin. The four corners of the pastry should hang over the edge.
Beat the mascarpone, soft cheese and sugar together in a large bowl, until smooth.
Beat in eggs, one at a time.
Add the Snickers slices and fold in.
Pour into a lined tart tin, and spread to the edges. Pull the corners of the pastry over the top of the dish, and brush with milk.
Place in the oven for 10 minutes, then lower to 180C/350F/Gas 4 for a further 25 minutes. Turn the heat back up to 200C/400F/Gas 6 and cook for a further 20 minutes until the pie is a golden colour.
Allow to cool before serving.