My solution to left-over egg whites: the most amazing, soft Amaretti biscuits. All you need is some almonds and sugar, and a leftover egg white! Any additions are optional: I’m using candied orange peel that I found in the cupboard (it goes so well with almonds), but you could add cocoa powder, matcha powder, chopped chocolate, lemon zest or a bit of cinnamon. The variations are endless.
If you want to make a vegan version, replace the egg white with 2 tbsp of aquafaba (chickpea water).