Preheat oven to 180 degrees C and grease a medium sized baking dish or 4 small baking dishes. Set aside.
Bring a large pot of salted water to a boil. When boiling, add dried pasta and 1/4 tsp salt and cook 1 minute less than the package directs for al dente.
Remove from heat, drain and rinse in cold water. Return to pot and set aside.
In a medium sized pot melt the butter.
Add flour, salt and freshly ground pepper, garlic paste and mustard powder and stir to create a roux. Stir over medium heat for one minute to let flour and butter settle together.
Slowly add about the hot milk a little bit at a time in order to create a smooth creamy sauce.
Remove from heat and stir in the sour cream and once well mixed, add the 1 cup of grated cheese.
Check the seasoning and add more if needed.
Stir in cooked elbow noodles.