Sift the flour into a bowl and rub in 3 oz / 85 g of the butter, until it resembles breadcrumbs. Mix in half the ground almonds, half the sugar and enough iced water to make a firm dough. Cover and refrigerate for 30 minutes. Handling it as little as possible, roll out the pastry, and use to line 12 greased and floured tart tins. Prick the base of each with a fork. Mix the rest of the almonds, sugar and butter together to form a paste. Divide amongst the tarts, and press into the base. Place a teaspoon of jam in each tart, place the tart tin on a baking sheet, and bake in the top of a preheated oven at 190°C / 375°F / Mark 5 for 15–20 minutes. Remove and allow to cool on a wire rack.