Melt the butter in a small saucepan over a very low heat; turn off and leave to cool down. In a bowl, beat the 2 whole eggs with the sugar. Gradually add the melted butter and, a little at a time, the flour sifted together with the baking powder. Continue stirring until the mixture is smooth and soft. Set aside 1/3 to decorate the top of the tart. Butter and flour a large baking tin: our friend Sonia (the recipe is hers!) uses a square one measuring 40x 40 cm. Spread the pastry out in it with your hands, until it covers the sides a bit as well. Now move on to the filling: melt the sugar and butter in a heavy-bottomed saucepan, over a low heat, stirring continuously When the mixture has caramelised, pour in the Vin Santo and stir until it evaporates. Tip the almonds into the pan and stir them in well, until the caramel begins to form “strands”. Now you have to work very rapidly: pour the almond mixture onto the pastry while still hot (and soft!), spreading it out evenly with a wooden spoon or a fork. Make strips with the pastry you set aside and lay them on top of the tart to create the decorative lattice. Use the prongs of a fork to “decorate” it even more by pressing them into the pastry around the edge; then brush it with an egg yolk beaten with a spoonful of milk. Bake in a preheated oven, at 180°C, for 20 minutes.