Boil water, add 1 tsp salt, cook penne pasta in it (8-9 min.) or as directed on pack. Drain water. 

Heat oil in non-stick pan, add garlic & mushrooms. Sauté mushrooms for 1-2 minutes and season it with salt and black pepper powder

To above sautéed mushrooms, add pasta Alfredo, milk and stir.  Add pasta to above sauce, toss and serve hot.