method
1. Wash the leeks well and cut them into 1 cm (3/8 in) slices.
2. Melt the butter in a saucepan on a moderate heat.
3. Put in the pine nuts and stir them around until they are beginning to brown.
4. Stir in the cumin and cook it for 1/2 minute.
5. Stir in the leeks and pour in the lemon juice.
6. Turn the heat down low, cover the pan and cook the leeks for 10 minutes.
