Finely crumble the amarettini (in a food processor or freezer bag and rolling pin). Mix very soft butter with the crumbled amarettini. Line a springform pan (26) with baking paper. Pour in the amarettini mixture and press firmly, forming a small edge.
Preheat the oven to 200 degrees.
Beat eggs with sugar until frothy (approx. 5 minutes), stir in the ground almonds, bitter almond oil and amaretto. Place on the amarettini base and smooth out.