Chop the bacon into 1cm pieces and add to a large saucepan or casserole dish. Cook for 5-10 minutes until the bacon is golden.
Chop the courgette into 1cm pieces and add to the saucepan along with the mushrooms (you can leave them whole unless there are any very large ones - cut those in half). Stir and let the vegetables heat through for 2 minutes.
Add the lentils and stock. Bring to the boil then simmer for 15-20 minutes until the lentils have started to soften.
Add the pasta and season with salt and pepper. Cook for another 10 minutes until the pasta is al dente. Turn off the heat and let it sit for 5 minutes before serving.