For the crust: 175g plain flour/ 6 ounces,115g /4 ounces butter, room temperature, 25g sour cream / 1 ounce
For the filling: About 6 medium tart apples, peeled, pitted and sliced, 3 large egg yolks 145g, sour cream/ 5 ounces (crème fraise), 150g granulated sugar / 5 and 1/3 ounces, 35g plain flour / 1 and a half ounces (about 1 heaping tablespoon)
For the glaze: 160g apricot preserves or jam / 5 ounces 1 tbsp Calvados (apple brandy) Whipped topping, for garnish.
For the crust: 1) Preheat the oven to 190°C/Gas 5 or 375ºF. 2) Place the flour, butter, and sour cream in a food processor and pulse to combine. 3) When the dough has formed a ball, pat with lightly floured hands into the bottom and sides of an ungreased tart pan with a removable bottom and 1cm sides, or a round au gratin dish. 4) Bake for about 18 mins, until the crust is set but not browned. Let cool while preparing the filling. 5) Lower the oven temperature to 180°C/Gas 4 or 350ºF.
For the filling: 1) Peel and thickly slice the apples. Arrange the apple slices in overlapping circles on top of the crust, until completely covered. Overfill the crust, as apples will shrink during cooking. 2) Combine the egg yolks, sour cream/crème fraise, sugar, and flour and beat until smooth. Pour the mixture over the apples. Place the tart pan on a baking sheet and bake for about 1 hr, until the custard sets and is pale golden in colour. Cover with an aluminium foil tent if the crust gets too dark. Transfer the tart pan to a wire rack to cool. When cool, remove the side wall of the pan. 3) To make the glaze, combine the preserves or jam and calvados. Spread with a pastry brush over the top of the warm tart. Serve the tart warm, at room temperature or chilled.
Variations: I like to add the zest of an orange or lime and some grated fresh ginger to the custard mixture.