Heat a frying pan or skillet over medium heat. Add olive oil to the hot pan followed by cubes of halloumi.
Fry for 3-5 minutes until browned and then flip and fry on the other side. Don't move them around, just let them sear and fry on one side before flipping and cooking the other side.
Transfer the pan fried halloumi from the pan to a baking sheet lined with paper towels to soak up any excess oil. Set aside.
Put the pasta on to cook according to package instructions. When cooked, drain the pasta, cover and set aside. If it starts to stick together at any point, add a little olive oil and toss it with the pasta.
While the pasta is cooking you can get started on your sauce.
Add butter to a pot on medium heat and let it melt.
Add chopped onion and sauté until the onion is softened.
Add crushed garlic and sauté with the onions.
Add sliced mushrooms and sauté until the mushrooms are softened.
Add all purpose flour and stir it in with the mushrooms. Sauté for 1 minute.
Pour in the vegetable stock and stir it in until well mixed.
Add soy sauce and dijon mustard and stir it in. Cook for 4-5 minutes until the sauce is thickened and has reduced a little.
Add the sour cream and stir it in. Simmer for a few minutes until thickened.
Add the pan fried halloumi and fold it in gently.
Add salt and pepper to taste.
Add the cooked pasta and fold it in gently.
Serve topped with fresh chopped parsley and a sprinkle of ground black pepper.