Chicken with Dijon and Vermouth

We made chicken as the main dish for the non-vegetarians amongst our guests for a groom's dinner that we hosted at our house, and it was delicious.  This variation of a classic French dish comes more or less from Diana Henry's From the Oven to the Table.

• 8 Skin-on, bone-in chicken thighs
• 4 tablespoon Dijon Mustard
• 1 tablespoon Extra Virgin Olive Oil
• Freshly Ground Black Pepper
• 3 Garlic Clove, finely grated
• 150 ml Dry White Vermouth 
• 1/3 cup sour cream or creme fraiche
• 2 tablespoon Finely Chopped Parsley
• Squeeze of Lemon Juice
• 10 g Unsalted Butter 

one. Preheat the oven to 190ºc.
two. Put the chicken thighs into a heavy roasting tin in which they can lie in a single layer, sitting snugly together with not much room around them, or into a 30cm shallow casserole.
three. In a small bowl, mix the mustard with the olive oil and spread this all over the skin of the chicken. Season with pepper (there's a lot of salt in the mustard). Mix the garlic with the creme fraiche and dollop it on top if the chicken (it doesn't have to be neat, as it will melt and run off the chicken once it goes into the oven). Pour in about 100ml of the vermouth, at the sides, so it runs underneath the chicken.
four. Cook for 40 minutes, adding the rest of the vermouth halfway through.
five. Put the chicken on a warmed plate and cover it with foil to keep warm.
six. Quickly bring the juices in the tin or casserole to boil and then reduce them a little so that they thicken. Add the parsley and lemon juice and whisk in the butter, bit by bit. Return the chicken to the sauce, then serve.