Coarsely grate sweet potato and zucchini/courgette. Slice spring onions and chop herbs if using.
Combine vegetables and herbs with eggs and flour. Season.
Heat oil in frypan. Cook mixture in batches. Drop in heaped spoonfuls of mixture and spread with back of spoon, approximately 5 fritters per pan. Cook until golden or about three minutes each side. Mixture should not squeeze out of fritter when pressed. Dress with slices of smoked salmon.
Combine sour cream with lemon juice to taste and serve with fritters (you could also use hummus, or a favourite dip mixed with a little plain Greek yoghurt).
Served in the photos with a rocket and tomato salad, dressed with balsamic vinegar and olive oil.