Lentil and smoked cheese lasagne

I'm a massive fan of the Good Food Channel (formerly UKTV Food). I can watch it for hours, much to Wikus's frustration. It is a great way to learn new techniques and the get inspiration for future recipes. This particular recipe was inspired by a traditional Italian lasagne - only without the meat.
Three vegetables form the base for a traditional lasagne sauce - the so-called "Holy Trinity" of onion, carrot and celery. In Italy, this mixture is called "soffritto". Instead of meat, I use lentils, and to add depth of flavour, I use smoked cheddar in the bechamel sauce and for the cheesy topping - infusing the whole dish with a delicious smoky flavour.

Ingredients
150g onions150g carrots150g celery4 cloves garlic600g tomato passata1 tablespoon tomato puree½ cup water200g green lentils / Puy lentils (dry weight)2 teaspoons dried oregano2 teaspoons sweet smoke paprikaSalt and pepperOlive oil250g lasagne sheets
Bechamel sauce
900ml milk50g butter50g plain flour250g grated smoked cheddar (reserve 100g for the topping)1 teaspoon Dijon mustardGround black pepper
Method
Place the dried lentils in a large pan and cover with lots of water (but no salt). Bring to the boil and then boil hard for 10 minutes with the lid off. Then turn the heat down, place a lid on the pan, and simmer for 30-40 minutes until the lentils cooked. Drain and then place to one side.
Chop the garlic and fry gently in olive oil. Finely dice the onions, carrots and celery and add to the pan. Cook gently for 10 minutes, stirring regularly. Add the passata, tomato puree and water. Add the oregano and paprika and then season to taste with salt and ground black pepper. Add the cooked lentils, place a lid on the pan, and simmer for 20 minutes.
Next, make the bechamel sauce. Heat the milk, either in a pan or in the microwave. In a separate pan, melt the butter and once it is bubbling, add the flour and stir with a wooden spoon. Cook the flour and butter for a couple of minutes to ensure the flour is cooked through. Then slowly add the hot milk, stirring vigorously to remove any lumps. Once you have a smooth sauce, add the mustard and plenty of ground black pepper. Then stir in 150g of the grated cheese until melted.
Finally, take a large lasagne dish and spread a thin layer of the lentil sauce over the base. Next, ladle a thin layer of the bechamel sauce over the lentils, and then cover with a layer of lasagne sheets. Repeat until you have three layers, and then top the last layer of lasagne sheets with a final layer of bechamel sauce. Sprinkle the remaining cheese over the top and then bake at 200C for 45 minutes until golden brown and bubbling.
Serves 6.