Grease and line a 20cm round, deep cake tin and put aside. Next, place the pears into a non-stick frying pan with 2 tbsp sugar and 2 tbsp water. Cover, then cook over a medium heat for 10 minutes until just tender, stirring every so often. Add the mixed spice and put aside. Place the butter, sugar, vanilla and ¼ tsp salt into a large bowl and beat till light and fluffy. Add the eggs, followed by the flour and beat until smooth. Next, fold in the ground almonds. Remove 85g of the cake mixture and put into a small bowl along with the 5 tbsp plain flour, 1 tbsp caster sugar and the chopped hazelnuts. Use your fingers to mix to a crumble and put aside. Spoon half the cake mix into the tin, top with ½ of the cooked pears, followed by ½ of the mincemeat. Repeat with the remaining cake mixture, pears and mincemeat. Scatter over the crumble topping and bake in the oven at 160`c for 1½ hours, covering with foil after 1 hour to stop the top from burning.