Chicken with a Mushroom, Pearl Onion and Tarragon Sauce

I originally found this recipe in a Cooking Light magazine. The first time I made this it was good but I felt it was a little lacking. I wanted some more sauce, more veggies and thought it would be great over some egg noodles. I remade this recipe and I am very happy with the results.
Enjoy!

Chicken with a Mushroom, Pearl Onion and Tarragon Sauce
 Serves 4

Ingredients 

2 cups unsalted chicken stock
3/4 carrot, cut into 1-inch pieces 
3/4 celery stalk, cut into 1-inch pieces
1/2 onion, cut in quarters
1 bay leaf
1 garlic clove, crushed
1 1/2  pounds thin sliced chicken breast
1/2 teaspoon sea salt, divided
1/2 teaspoon black pepper, divided 
3 tablespoons all-purpose flour
2 tablespoons olive oil, divided 
2 teaspoons butter, divided
1 8 oz packs bella mushrooms, quartered
3/4 cup frozen pearl onions, thawed and drained
1 tablespoon water
1 tablespoon cornstarch
1 tablespoon chopped fresh tarragon
8 oz wide egg noodles, cooked without salt or fat

 Preparation

1. In a small saucepan bring chicken stock, carrot, celery, onion, bay leaf and garlic to a boil. 
2. Cook 6 minutes or until reduced to 1 1/4 cups. Strain and keep the liquid from the stock mixture. Discard the veggies and seasonings.
3. Sprinkle the chicken evenly with 1/4 teaspoon salt and 1/4 teaspoon pepper. Place flour in a shallow dish; dredge chicken in flour. Heat a large skillet over medium-high heat. Add 1 tablespoon oil and 1 teaspoon butter to pan; swirl the pan until butter melts. 
4. Add half the chicken to the pan; cook 3 minutes on each side or until golden. Remove the chicken from the pan; keep chicken warm. Repeat procedure with remaining 1 tablespoon oil, 1 teaspoon butter, and chicken.
5. Return the skillet over medium-high heat. Add mushrooms and onions; cook approx. 7 minutes or until browned, stir occasionally. 
6. Add the reserved stock mixture; bring to a boil, scraping the pan to remove any browned bits of chicken or veggies. 
7. Combine 1 tablespoon water and cornstarch in a small bowl to create a slurry. 
8. Stir the slurry into the boiling stock mixture; cook 2 minutes to thicken sauce and cook the starchy taste away. 
9. Stir in remaining 1/4 teaspoon salt, remaining 1/4 teaspoon pepper, and tarragon. 
10. Place noodles on plate, then place chicken over noodles, spoon sauce over chicken.

Note: To save money you can buy regular boneless skinless chicken breasts and slice them in half horizontally.