Green bean casserole with mushrooms

Method

1. First make the roux. Melt the butter and cook the flour in it for 2 minutes on a low heat, stirring occasionally. Use as required. Roux can be stored in a cool place and used as required or it can be made up on the spot if preferred. It will keep at least a fortnight in a refrigerator.

2. First, make the mushroom sauce. Melt the butter in a heavy saucepan until it foams. Add the chopped onions, cover and sweat on a gentle heat for 5-10 minutes or until quite soft but not coloured. Meanwhile cook the sliced mushrooms in a little butter, in a hot frying pan in batches if necessary. Season each batch with salt, freshly ground pepper and a tiny squeeze of lemon juice. Add the mushrooms to the onions in the saucepan, then add the milk and cream and allow to bubble for a few minutes. Thicken with a little roux to a light coating consistency. Taste and correct the seasoning.

3. Next, cook the crispy onions. Melt the butter in a sauté pan, add the olive oil, toss in the onions and cook stirring regularly on medium heat until golden and crisp — 10 minutes approximately.

4. Meanwhile, prepare and cook the beans. Choose beans of a similar size. Top and tail the beans. If they are small and thin leave them whole, if they are larger cut them into 2.5- 4cm (1- 1½ inch) pieces at a long angle.

5. Bring the water to a fast-rolling boil, add 3 teaspoons of salt then toss in the beans. Continue to boil very fast for 5-6 minutes or until just cooked (they should still retain a little bite). Drain immediately. Taste, season with freshly ground pepper and a little sea salt if necessary.

6. To finish, heat the mushroom sauce, stir in the beans and transfer to a gratin dish. Sprinkle the top with crispy onions and flaked almonds and heat through in a moderate oven for 5-10 minutes.