Pour a kettle of boiling water over baby spinach in a colander. When cool enough to handle, squeeze out any water – do this really well or your falafels will be too soft. Pulse in a food processor with drained chickpeas, feta, cumin and plain flour until just combined. Roll into tbsp-sized balls with wellfloured hands, then flatten into patties.
Fry in batches in vegetable oil for 2-3 mins each side, then leave to cool. Place on a baking tray, cover with cling film and freeze. To serve, defrost in the fridge overnight and cook at 180C/160C fan/ gas 4 for 5-10 mins. Serve with tzatziki.
These canapés can be frozen for up to 3 months. If you're short on baking trays, then once the canapés are frozen solid, transfer them to freezer bags. Make sure they are well wrapped or sealed to preserve them properly. Label everything clearly to remind yourself what you've frozen.