Cook the bacon. In a large skillet over medium-high heat, cook the chopped bacon for 4–5 minutes until crisp. Remove with a slotted spoon and set aside, leaving the drippings in the pan.

Sear the chicken. Pat the chicken thighs dry and season with salt and pepper. Add the butter to the skillet, then sear the chicken over medium-high heat for about 6–7 minutes per side, until golden and crisp at the edges. Work in batches if needed. Transfer the chicken to a plate.

Sauté the aromatics. Add the chopped onions and minced garlic to the same skillet. Cook for about 3 minutes, stirring often, until softened and fragrant.

Add the potatoes. Stir in the potatoes and cook for about 10 minutes over medium heat, stirring occasionally, until they start to soften and lightly brown.

Build the sauce. Stir in the Dijon mustard, thyme, and tarragon. Pour in the water (or chicken broth) and heavy cream. Bring to a gentle simmer, scraping up any browned bits from the bottom of the pan.

Finish cooking. Return the chicken and bacon to the skillet. Simmer uncovered for about 15 minutes, until the sauce thickens slightly and the chicken is cooked through.

Serve. Sprinkle with fresh parsley and serve warm with mashed potatoes, rice, or crusty bread.