Preheat oven to 125C/gas 1. Process biscuits (or crush) until crumbs. Add skinned hazelnuts. Melt butter in pan and add biscuit crumbs and nuts. Cook until melted and amalgamated together (2 or 3 minutes only). Sit 6x4 inch round pastry cutters on a baking sheet. Press the biscuit base evenly into them (using the back of a spoon to compact it). Chill well. Prepare cheesecake. In a large shallow bowl beat together cheese, lemon zest and juice, vanilla and stem ginger (finely chopped) until light and smooth. Whisk eggs and sugar in a mixer until it forms a thick heavy trail. Gently whisk egg mixture into cheese using a spatula or balloon whisk until blended but still light and fluffy. Pour cheesecake on to biscuit bases in prepared rings and bake in preheated gentle oven for about 20-25 minutes until only just set. (They will continue cooking as they cool down). Whilst only just warm spread with the sour cream and allow it to set and become glossy. Julienne some lemon zest and cut a piece of stem ginger into fine julienne. Blanch the lemon zest and ginger and whilst still warm but soft toss in caster sugar. Leave in a dry place to crystallise and firm up. Serve with a small piece of lemon and ginger on top and a drizzle of lemon sauce around. A sprig of sweet cicely would finish this dessert off.