01 - Pat the chicken breasts dry with paper towels and season both sides generously with salt and freshly ground black pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Add the chicken breasts and sear until golden brown, about 4 minutes per side. Remove the chicken from the pan and set aside on a plate.
03 - In the same skillet, add the chopped onion and cook until softened, about 3 minutes. Stir in the minced garlic and cook for an additional 1 minute until fragrant.
04 - Reduce the heat to medium. Stir in the Dijon and wholegrain mustards, mixing thoroughly with the onion and garlic until well combined.
05 - Pour in the chicken stock and bring to a gentle simmer, using a wooden spoon to scrape up any browned bits from the bottom of the pan.
06 - Stir in the heavy cream and honey until the sauce is smooth. Return the seared chicken breasts to the skillet, spooning the sauce over the top.
07 - Simmer uncovered for 15 to 20 minutes, or until the chicken is cooked through (internal temperature reaches 165°F) and the sauce has thickened to a rich consistency.
08 - Stir in the chopped tarragon, adjust seasoning with salt and pepper to taste, and garnish with fresh chopped parsley before serving.