Add the pasta to a large pan and simmer (time will depend on brand - check packaging). Pasta can cook while you prepare the sauce.
In a medium saucepan, melt your butter. If using mushroom and onion, add these and gently saute for a few minutes.
Whisk together the flour and milk until smooth, in a bowl.
Add this to your saucepan and stir. Make sure the heat is medium - not boiling. You should find that after a minute the sauce starts to slowly thicken.
Add your nutritional yeast, mustard, garlic and salt to the saucepan. Whisk frequently - don't let the sauce stick to the bottom!
After about 5 minutes, your sauce should have thickened. Feel free to adjust to preference - you can add more almond milk to thin out.
Add the cream cheese to the saucepan and stir in, allowing it to melt. Ensure the sauce does not boil.
It's ready! Merge your pasta with the sauce and serve. We like ours with cracked black pepper and a sprinkle of cheese on top.