Heat oven to 160C/fan 140C/gas 3 and lightly butter a 20 x 23 cm shallow baking tin. Sift the flours together, then stir in the sugar, almonds and a pinch of salt. Rub in the butter and vanilla seeds to make fine crumbs, then tip into the tin and press down with the back of a spoon. Put in the freezer for 5 mins, then bake for 35-40 mins. Cool.