Rinse and pat dry the chicken tenders. Sift together the flour, chicken seasoning, tarragon, seasoned salt, garlic powder, onion powder and dry Italian seasoning. Remove 1/4 cup and set aside.
Dredge the chicken in the remaining seasoned flour.
Heat a couple of drizzles of olive oil in a large skillet over medium-high heat. Cook the tenders for 2 minutes per side or until the juices run clear. Remove to a platter and keep warm.
Add a few drizzles of olive oil and Tbsp of butter to the pan. Cook the sliced mushrooms and onions. for 5-7 minutes until softened and browned. Scrape any brown bits from the bottom of the pan. Season with salt and black pepper to your taste.
Sprinkle the remaining 1/4 of flour over the cooked mushrooms and onions, Stir until all liquid is absorbed.
Whisk in the the milk. Bring to a simmer stirring constantly and cook until thickened. Lower the heat and allow to bubble gently for 5 minutes.
Pour over the chicken pieces and serve.