Toast the almonds for a few minutes in a preheated oven at 200 C°. Grind them in a mixer with bitter almonds, caster sugar and powdered sugar, then sift the mixture and grind it for a second time. Then fold the egg whites in and mix all the ingredients with a spatula.
Cover the mixture with a clean tea towel and place it in the fridge for about 4-6 hours. Line two baking tray with parchment paper and lightly brush it with butter, then take the amaretti mixture out of the fridge and make about 50 little balls. Press them down to give them the amaretti's traditional shape, place them on the tray and bake them in a preheated oven at 170 C° for about 20 minutes (at 150° for 15 minutes if in a convection oven).
Once they have cooled down, serve with a top Italian dessert wine, try them with moscato bianco.