I’ve served this Leek Gratin dish several times and I always get great feedback for it. I suppose it’s because it’s not overcooked or watery and tastes great
This cheese sauce is very versatile and I use it all the time for recipes like baked macaroni cheese and cauliflower cheese
Preheat the oven to 180 C
Top and tail the leeks, slice in half lengthways and rinse until running water to clean. Cut the leeks in half cross wise
In a pan of boiling salted water, add the leeks and bring back to the boil. Cook the leeks for about 5 minutes, drain in a colander and then rest on paper towels to remove as much liquid as possible
In a saucepan, add the butter and start to melt and add the onions to the pan and start to soften. This will take about 5 minutes
Add in the garlic and cook for a further few minutes over a low heat. Then add the mustard, mix together and cook for another minute
Now add the flour and bring the mixture together and cook for a few minutes
Gradually pour in the milk and keep stirring as to remove lumps. The sauce should be looser/thinner than a standard white sauce. If you need more milk as it's too thick then gradually add some extra
Remove the sauce pan from the heat and add the grated Cheddar cheese. Stir until the sauce is smooth and thickened
Butter a baking dish large enough to hold the leeks and cheese sauce. Add the leeks and then pour over the cheese sauce to cover
Blitz the sliced bread in a blender to make fresh bread crumbs
Melt the butter in a saucepan and when melted, pour in the breadcrumbs, remove from the heat and stir until the butter has coated the breadcrumbs evenly
Sprinkle the breadcrumbs over the leeks and cheese sauce dish. Cover with tin foil
At this point you can keep the dish in the fridge until you’re ready later on in the day
To serve, heat the oven to 180C and cook the dish for 30 minutes