Step 1

Bring the milk to the boil in a saucepan, add 2 of the bay leaves and the black peppercorns. Flatten, but don’t peel the garlic. Add to the milk, then remove from the heat, cover with a lid and set aside to infuse.

Step 2

Trim the leeks, discarding the root and the very thickest tips. Cut into 2cm lengths and wash very thoroughly in cold running water. Pack the leeks into a medium-sized saucepan, add half of the butter the vegetable stock or water. Season lightly with salt and the lemon juice and 2 more bay leaves.

Step 3

Bring the leeks to the boil, lower the heat and partially cover with a lid. Let the leeks cook over a moderate heat, lightly bubbling, for 12-15 minutes until they are tender to the point of a skewer and the cooking liquor has almost evaporated.

Step 4

Cook the gnocchi in boiling, lightly salted water and drain. They are done when they bob up to the surface.

Step 5

Preheat the oven to 200C/gas mark 6.

Step 6

Melt 35g of butter in a medium-sized pan over a moderate heat, then stir in 35g of flour. Continue stirring for 3 or 4 minutes until you have a pale, smooth paste. Stir in the infused milk with a wooden spoon, a little at a time, holding back the bay leaves and garlic as you go. Let the sauce come to the boil, stirring continually until thick and creamy. Whisk out any lumps with a balloon whisk. Stir in the double cream, the leeks, mustard and chopped parsley.

Step 7

Put half the sauce into a baking dish, add the gnocchi, then add the remaining sauce. Grate a fine layer of parmesan over the surface and bake for 30 minutes until bubbling and the surface is patchily golden.