Heat a dutch castiron on medium heat. Add olive oil, once hot, add crushed red pepper flakes. Saute for about 30 seconds.
Add sliced mushrooms. Saute for 4 minutes.
This is what you should have.
Add the pasta to the boiling hot water. Season with salt. Follow the instructions on the back of the package. I prefer whole wheat pasta, however, regular white or gluten-free pasta will work too.
Now add the chopped spinach to the mushrooms. Stir. The spinach will take about 1 minute to wilt.
Add the garlic and sun-dried tomatoes. Stir and cook for 2 minutes.
Add unsalted butter.
Once butter melts, add whole wheat flour (Indian flour works too).
Stir the butter and flour and cook for 1 minute.
Now VERY SLOWLY, add whole milk (2% reduced-fat milk will work too) to the veggies while stirring the veggies into the milk mixture. Make sure you add the milk slowly to avoid curdling.
Continue adding milk - you'll need 3 cups total.
Season with salt and add black pepper.
Allow the milk mixture to come to a slight boil. You'll see bubbles starting to form.
Add the pasta to the sauce.
Give it a good stir.
Add parmesan cheese and starchy pasta water. The starch will help thicken the sauce and help the pasta cling to the sauce.
Top with fresh basil. Stir.