Bring a pot of salted water to a boil. Once boiling, place the potatoes in the water. Bring the water to a steady simmer and allow the potatoes to cook for about 10-15 minutes or so, or until you can just pierce one of the largest potatoes with a fork. Remove the pot from the heat but leave the potatoes in the pot with the hot water for 10-15 minutes. Drain the potatoes in a strainer and allow them to cool slightly while you prepare the chicken.
Preheat your oven to 400 degrees Fahrenheit. In a bowl, combine the mustard, honey, garlic, tarragon, salt and pepper.
Toss the chicken thighs in the ½ tsp. black pepper and ¼ tsp. salt, along with half of the mustard mixture. Allow the thighs to marinate for 10-15 minutes or so while you finish preparing the potatoes.
Take the potatoes from the strainer and slice the large ones in half. You can keep any potatoes about the size of your thumb or smaller whole. Toss the potatoes in the melted butter, thyme leaves and a pinch of salt and pepper.
Arrange the chicken thighs on a large sheet pan with the potatoes surrounding them. Make sure the chicken is skin side up, and try to keep the potatoes cut side down. Place fresh tarragon sprigs all around the pan.
Roast the pan in the oven for 30-35 minutes. Remove the pan from the oven and pour or rub the remaining mustard sauce on top of each piece of chicken. You can do this with the back of a spoon or a small basting brush. Place the chicken back into the oven and roast for an additional 10-15 minutes, or until the internal temperature of the chicken thighs are around 175 degrees Fahrenheit. Allow the chicken to cool slightly, then plate the chicken and potatoes and enjoy!
Stone ground grainy mustard is key here as it will provide a nice tang and texture to the chicken. If you want the chicken to be even more flavorful, you can marinate the chicken in the fridge for an hour or so prior to roasting.
Parboiling the potatoes prior to roasting them provides the most perfect crispy potatoes on the outside while being super tender on the inside. I haven’t tested this recipe without the parboiling, but I imagine you could make this dish without the boiling by cutting your small potatoes into rounds or discs and roasting them on the sheet pan with the chicken that way.
For extra flavor, toss some thinly sliced red onion in with the potatoes and butter and add them to the roasting pan.