Coarsely mash the amarettini and place in a bowl. Process into crumble with the almonds, sugar, butter and lemon zest. Whisk and mix in the egg yolks so that the dough just sticks together.
Halve the peaches, core them and drizzle the cut surfaces with lemon juice. Spread the amarettini mixture on the peach halves and press down lightly.
Cut the aluminum foil into 6 pieces approx. 20 cm long. Place 2 peach halves on each piece of foil, fold up the ends of the foil and gently press together to form a loose package. Grill over high heat for 15 minutes until the peaches are soft and the filling sizzles.