Boil water in a pot, add oil and salt, add spaghetti, and cook it for 7-8 minutes till al dente. Retain some pasta water in a glass, rest throw it away, and let the pasta cool down.
Wash the mushrooms properly, cut them in halves, and boil them in a pot for 5-8 minutes in a mixture of water and salt. Seive away the water.
Heat up oil in a skillet, and sear the mushrooms on medium flame till they get brown. Then keep them aside on a plate.
In the same skillet, add butter, refined flour, and milk in 3 batches of equal amounts (100 ml each). Whisk them properly in each round to get a lump-free sauce at the end.
Add salt, oregano, grated mozzarella, and red chili flakes. Mix well.
Then add mushrooms and pasta, and coat them well with the sauce.
Finally, adjust the saltiness of the pasta and garnish it with grated mozzarella, oregano, and red chili flakes. Also, you can sprinkle chopped parsley on top for some freshness.
Your mushroom alfredo pasta is ready to be served.