
In a large deep pot, heat 1 tablespoon olive oil over medium heat. Season the chicken with ½ teaspoon salt and pepper. Add about half the chicken to the hot oil and cook for 2–4 minutes per side, or until golden brown. They won't be fully cooked. Remove with a slotted spoon and set aside. Add the remaining chicken and repeat the cooking process. Set the browned chicken aside.
To the same pot, add the remaining olive oil along with mushrooms and onions. Cook for 7–9 minutes, stirring often, or until the mushrooms release most of their moisture and the onions soften. Add garlic and cook for 30 seconds, or until fragrant.
Sprinkle the flour and paprika all over the mushrooms and onions, then stir to evenly coat. Cook for 1 minute, then add the chicken stock and Dijon mustard. Bring to a boil, whisking to get rid of any lumps. Season with the remaining salt and add chicken back to the pot. Then, reduce the heat to a simmer and cook, stirring often, for 15 minutes or until the sauce thickens.
Remove from heat and whisk in the Greek yogurt until smooth. Sprinkle with parsley and stir to combine. Serve over warm buttered noodles.