Preheat Oven to 400°F
Chop bratwurst in halves, so take the 4 bratwurst cut in half and you should have 8 smaller pieces.
Heat 2 tablespoons of the oil in a 12 inch cast iron skillet or pan ( I use Rachael Ray 3.5-Qt Cast Iron Braiser) heat over high heat until smoking lightly about 3 minutes.
Sprinkle chicken thighs with salt and pepper to taste on skin side then add them to the very hot Braiser/skillet skin side down.
Lower heat to medium and cook without turning until the skin renders its fat, becomes brown and crips and releases easily from pan which takes about 10-12 minutes.
Move the thighs to the edge of the pan so you are making a circle around the edges with chicken.
Add Onions and 2 garlic cloves and the pancetta. Cook until tender and translucent, about 5-6 minutes, stirring frequently. Stir in 2 Tablespoons bread crumbs.
Reserve 1/2 cup of the beans and mash with fork or potato masher in small bowl, making a sort of paste.
In the pan with the chicken, stir in the remaining beans, chicken broth/stock, thyme springs and Bay leaves. Season with salt and pepper to taste.
Stir in the mashed beans that you have reserved, add the bratwursts, stir to blend items together.
Take the chicken and put them skin side up now in the mixture of beans and brats. Bring to a simmer about 5 minutes.
Place the pan on the top rack of the oven and cook until the chicken is fully cooked and the sauce has thickened about 30 minutes.
Remove the pan from the oven and set the broiler on HIGH
Grate the remaining 2 garlic cloves on a small grater ( I use the Rachael Ray Multi Stainless Steel Grater ) into a small bowl along with the remaining breadcrumbs and the chopped thyme leaves.
Sprinkle the mixture over the cassoulet and broil on top rack about 3 minutes until golden brown.
Pull out of the oven and let cool 10 minutes before serving