Heat your oven to 200°C/Fan 180°C/Gas 6. Peel the onions and thinly slice them. Peel the garlic cloves and finely chop or grate. Cut the broccoli into florets, and slice the stalk into small pieces.
Pour 1 tbsp oil into a deep, ovenproof frying pan (see our tip if your pan's not ovenproof) and bring to a medium heat. Slide in the onions, half the garlic and a generous pinch of salt and pepper. Fry for 3-4 mins, till slightly softened. Stir in 1 tbsp flour, coating the onions, and continue to cook for another 2 mins.
Pour 100ml of the cream into the pan and top up with 100ml boiling water. Stir well to combine and beat out any lumps. Grate the cheddar and stir into the sauce till melted and thick. Bring to a simmer. Tumble the broccoli into the sauce and turn over till all of the florets are coated. Transfer the pan to the oven and cook for 20 mins, till golden on top.
While the broccoli cheese is cooking make the lentil salad. Drain the lentils into a sieve and give a good rinse, then shake dry and tip into a large bowl. Wash the carrots and their tops, then separate the greens from the carrots. Peel the carrots, and use the veg peeler to shave ribbons off them, chopping the carrot cores when you've peeled down to them. Finely chop the carrot tops, and add both to the lentils.
Roughly chop the tomatoes into small pieces and slide into the lentils and carrot bowl. Add the remaining grated garlic, 1 tbsp each cider vinegar and olive oil, and a good pinch of salt and pepper. Stir to combine.
Serve generous helpings of the rich broccoli cheese with the carrot lentil salad heaped up on the side.
Frying pan not ovenproof?^
Make your cheese sauce using a regular pan, then spread the sliced broccoli into a casserole dish and pour the sauce over the top. Swirl till everything is coated, then roast in the oven till golden on top.