In a large saucepan of boiling salted water, cook the pasta according to the package directions. Drain well.
In a large skillet, heat olive oil on medium-high heat. Cook ground beef until it is browned. Drain any excess fat and place in a bowl.
Add diced onion to the skillet and cook for 2 mins, stirring often. Cook for about one minute more.
Mix flour in until it is lightly browned. This should take about one minute.
Slowly add the beef stock. Stir to combine. Mix in marinara sauce. Stir in dried parsley, oregano and paprika.
Bring to boil. Reduce heat and simmer for 6-8 minutes, stirring occasionally.
Mix in the cooked pasta and return the beef.
Stir in the heavy cream and continue stirring for about 1-2 minutes. Adjust salt and pepper to taste.
Stir in the sour milk.
Next, add the cheddar cheese and stir until it is melted. This should take about 1-2 minutes.
Serve immediately garnished with parsley, if desired