In a medium frying pan, heat the butter over moderate heat. Season the chicken with 1/4 teaspoon of the salt and the pepper and add it to the pan. Cook the chicken until brown, about 5 minutes. Turn and cook until just done, 4 to 5 minutes longer. Remove the chicken from the pan and put it in a warm spot.
Reduce the heat to moderately low. Stir in the onion and cook until starting to soften, about 2 minutes. Sprinkle the flour over the onion and stir to combine. Increase the heat to moderate; whisk in the wine and the tarragon, and cook until the sauce starts to thicken, about 2 minutes. Stir in the cream, the remaining 1/2 teaspoon salt, and any accumulated chicken juices. Serve the sauce over the chicken.
Menu Suggestions: Rice along with a simple vegetable such as steamed asparagus or sautéed zucchini and carrots would round out the meal nicely.
Wine Recommendation: The richness of the cream sauce will contrast well with a fresh white wine from the north of Italy. Try a tocai friulano, pinot grigio, or pinot bianco from an area such as Collio or the Alto Adige.