To make the dough: put the butter or margarine in a bowl with the dry ingredients and mix. Add the beaten egg, and mix until the mixture begins to form a ball.
Gather the dough into a ball with the fingers and then knead well until smooth and free from cracks; if it is very dry, you can add a little milk or water.
Heat oven to 160°C fan.
Flatten the ball into a block about 2cm thick. If not using immediately, refrigerate.
Roll it out until it is about 1 cm thick and use it to line a 25cm tart tin. Refrigerate until firm — about 30 minutes and then line the tin with baking parchment, fill with baking beans and bake the case for 15 minutes with the beads, when the edges should look lightly golden. Remove the beans and bake for a further 5 minutes until the base is sandy to feel and golden.
Cool in the tin on a rack.
For the filling: make a caramel by melting the sugar and butter into a large non-stick pan, mixing regularly.
When it’s a caramel color, take the pan off the heat and carefully stir in the cream — it may spit and bubble. Mix well. Don’t worry if it’s a little lumpy at first, you may need to warm it up gently, stirring continuously until the cream binds with the sugar and is smooth.
Add the nuts and stir. Pour over the cooked base and decorate with the whole pecans. Bake at 180°C for 2 minutes or until golden and bubbly. Decorate with the extra pecan nuts and allow to cool slightly before eating.