Pour the milk in a microwaveable dish and add the half onion, peppercorns and bay leaf. Microwave until warm.
Melt the butter in a pan and then add the flour. Stir until it is well combined.
Add the milk a little at a time (use a sieve) and whisk until it is absorbed. Do this until all the milk has been used. Simmer gently for a few minutes.
Add the cheese and whisk until it has melted. Season the sauce with salt and pepper. Keep it warm until it is required.
Once you have started the sauce. Cook the pasta according to the instructions.
Saute the mushrooms in the olive oil with the garlic until they are soft and juicy. Season with lots of black pepper for a fabulous flavour.
Rinse the spinach in a colander, then pour over a kettleful of boiling water to wilt the spinach.
Pour a little cold water on, so you do not burn your hands, then squeeze out the excess liquid. I like to pat it dry with a teatowel as well before chopping it.
Once the pasta is ready, drain it, then coat in the cheese sauce and stir through the spinach and mushrooms.
Serve in bowls topped with crumbly feta cheese and a good grating of black pepper.