Bring 4 to 5 cups water to a boil in a large pot along with salt.
When the water begins to boil rapidly then add pasta and cook al dente.
Drain off completely reserving 2 to 4 tbsp of water.
If using veggies, chop them and set aside. You can also use frozen mix veggies like carrots, peas and sweet corn.
Making sauce for white sauce pasta
Add half of the butter to a pan and saute vegetables until al dente. Set these aside.
Set the flame to low. Add rest of the butter to the pan and add flour. You can also add more butter than mentioned in the recipe.
Saute it in butter until the raw smell goes off. The flour may turn slightly lumpy. Just break up the lumps and continue to saute until it no more smells raw. Make sure the color of the flour doesn't change.
Pour ¼ cup of milk. Stir well continuously breaking up the lumps.
When you see the flour is well blended with milk, pour rest of the milk and mix well.
Cook this until the sauce turns slightly thick.
Add cheese if using and gently stir until the mixture reaches a thick sauce consistency. Add oregano and pepper. Switch off the stove.
For making white sauce pasta
Add more salt if needed along with veggies & cooked pasta.
Mix well to coat the pasta with the creamy sauce. If the sauce is too thick then, you may add 1 to 2 tbsps of reserved hot pasta cooked water.