Pat the chicken thighs dry with paper towels and season generously with salt and pepper on both sides.

Heat olive oil in a large Dutch oven or heavy-bottomed pan over medium-high heat. Add chicken thighs skin-side down and cook for 6-7 minutes until golden brown. Flip and cook for 3 minutes more, then transfer to a plate.

Reduce heat to medium and add 1 tablespoon butter. Add the new potatoes and baby carrots, cooking for 5 minutes until lightly coloured. Add the turnips and cook for 2 minutes more.

Add the shallot and garlic, cooking for 1 minute until fragrant. Pour in the white wine, scraping up any browned bits from the bottom of the pan.

Add the chicken stock, thyme, tarragon, and bay leaf. Nestle the chicken thighs back into the pan, skin-side up. Bring to a simmer, then reduce heat to low, cover, and cook for 20 minutes.

Add the green beans, cover, and cook for 10 more minutes. Add the peas and cook uncovered for 5 minutes until all vegetables are tender and chicken reaches an internal temperature of 75°C when tested with a meat thermometer.

Remove the herb sprigs and bay leaf. Stir in the remaining butter and Dijon mustard into the sauce. Taste and adjust seasoning with salt and pepper.

Serve the chicken and vegetables in shallow bowls, spooning the sauce over the top and garnishing with fresh chopped parsley.