In a large skillet, melt 2 tablespoons butter over medium-high heat.
Saute the chicken and mushrooms for 5-6 minutes, or until no pink remains in the chicken.
Remove the chicken and mushrooms from the skillet; discard the pan juices.
Add the remaining butter, flour, salt, and pepper to the skillet; cook, whisking constantly, until the butter melts.
Slowly add the chicken broth and cream; bring to a boil, whisking until smooth and thickened.
Reduce the heat to medium-low, return the chicken and mushrooms to the skillet; add the peas and pimientos.
Simmer until heated through, stirring constantly.
Serve immediately.