Serves 8-10
adjust servings:

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  1. Preheat the oven to 180˚C/160˚C fan/gas mark 4. Coat a baking dish with cooking spray and fill a large bowl with ice water.
  2. Bring a large pot of water to a boil. Add the green beans and boil for one minute, then transfer to the bowl of ice water. Leave for 3-4 minutes, then drain and pat dry with kitchen paper. Dry the bowl and return the green beans to it.
  3. Melt 20g of the butter in a pan over a medium-low heat. Cook the mushrooms and onion for 5-6 minutes until soft, stirring occasionally. Transfer to the bowl with the green beans.
  4. Melt 60g of the butter in a small saucepan over a medium heat. Add the garlic, then whisk in the flour until smooth. Cook, whisking constantly, for 30 seconds. Whisk in the stock and milk (or cream).
  5. Bring to a gentle simmer and continue whisking constantly until thickened. Remove from the heat and stir in the Greek yoghurt and some salt and pepper. Let the mixture cool for 5-6 minutes, then whisk in the egg.
  6. Pour sauce into the bowl with the green beans and mushrooms. Stir gently to combine. Transfer to the prepared baking dish.
  7. Melt the remaining 20g of butter and stir into the breadcrumbs. Stir in the grated Cheddar, then scatter the mixture over the top of the casserole.
  8. Bake for 45 minutes, until golden on top and bubbling around the edges. Check after 25 minutes and cover with tin foil if the top is browning too quickly. Allow to stand for 10 minutes before serving.

Vegetable stock can be used as an alternative to Chicken stock, if you wish.
Cream can be used as an alternative to Whole milk, if you wish.

Nutrition Facts

Per Serving 207kcals, 10.5g fat (6.1g saturated), 21.3g carbs, 4.5g sugars, 8.5g protein, 4.2g fibre, 0.325g sodium


Make the casserole as far as Step 6 the day before Christmas. On Christmas Day, allow it to stand out of the fridge for one hour before baking, topping with the crumb mixture just before it goes into the oven.