Preheat oven to 400℉
In the dutch oven, melt another 2T butter.
Season Chicken with Salt & Pepper.
Coat the Chicken Legs in the flour and add to the pan.
Pan fry each side until golden brown and crispy, about 7-8 minutes per side.
Remove from pan and set aside.
Melt another 2T butter in the pan, adding it to any chicken fat or bits that have stuck to the pan.
Cut Onions in half and slice into 1/4" slices. Add to the pan and fry for 7-8 minutes, until translucent.
Add the Garlic. Stir in with Onions and cook for a minute or so, until fragrant.
Add Thyme sprigs.
Add the Calvados Brandy to deglaze the pan. Stir, scraping bits from the bottom.
Add Cider. Heat until simmering, creating a sauce.
Nestle the Chicken into the sauce. Cover and cook in oven for 50-60 minutes, until chicken is very tender, and starting to fall off the bone.