Fill a large pot ⅔ with water, place 1 teaspoon salt and bring to a boil on high.
Bring temperature down and put in tagliatelle. If they are knit tightly in circles, slightly break them up. Follow the directions on the bag for how long to cook them. (Mine took 14 minutes.) Stir every few minutes.
Drain and return to the pot. Add ¼ teaspoon salt and butter and stir. Add milk and stir again.
Once combined, add sour cream and stir. Grate feta cheese over the pasta, and stir again until everything is evenly mixed.
Serve warm.
Notes
Add more sour cream and cheese if you prefer. Also, if you like meat, you can prepare chicken and or a schnitzel on the side.