In a large heavy bottom skillet or braiser with a tight fitting lid, heat tbsp of olive oil over medium/high heat.
In a small bowl mix together paprika, salt and better. Pat dry the chicken thighs and season them generously with the seasoning mixture. Place the thighs 4 at a time skin side down into the pan. Allow the skins to brown (about 4-5 minutes) then turn and continue to cook for 3 more minutes. Remove from pan, set aside and repeat the process with the remaining thighs.
Add shallots to the pan and allow to cook at medium heat until just tender.
Add 1 cup of the chicken stock to the pan along with the dijon mustard. Bring to a simmer, stirring to scrape up brown bits and incorporate ingredients. Allow to continue simmering until sauce reduces to about 1 cup and thickens enough to lightly coat the back of a wooden spoon. Remove from heat and slowly whisk in cold butter. Once incorporated add lemon juice, capers and tarragon.
Add the kale and spinach to the pan and toss until greens are lightly coated with the sauce. Add the chicken back to the pan, tucking each thigh into the greens. Drizzle the remaining broth over the entire dish, cover and return to low heat. Braise the mixture over low heat for 30 minutes.
While the dish is just fine as is, I like my skins a little crispy. If you want to take the extra step for good crispy skins, place the entire dish under the broiler for 3 more minutes, or until skins start to bubble.
Serve over mashed potatoes or a bed of creamy polenta. Enjoy!