Preheat an oven to 170FAN (about 375 Fahrenheit).
In a large, oven-safe pan or skillet, over medium high heat, brown the sausage. Once it's browned, remove it from the pan and set it aside. Next, brown the chicken. Once it's browned on the outside, remove it and set it aside. *Don't worry about cooking the meat all the way through, just get it seared a bit on the outside. It's going to get cooked through when we bake everything together.
After you remove the chicken, add a pad of butter (about 1 tbsp) to the hot skillet. It will begin to melt immediately. Add the chopped onion and stir to coat the onion in the butter and any drippings from the browned meat.
Saute the onion for about 5 minutes, until it's just softened, and then add the bell pepper and stir.
Add the garlic and stir. Saute for about 2 minutes, until the garlic is slightly fragrant.
Add the chili and stir. Saute for about 1 minute.
Add the paprika, dried oregano, salt and pepper, and stir to coat the veggies in the spices.
Add the tomato paste and stir to distribute it as evenly as you can.
Add the rice and stir to combine everything together.
Add your liquids: add the saffron and its' steeping liquid, the can of tomatoes and the chicken stock. Stir to combine.
Add the meat to the rice and veggie mixture and stir to combine.
Add a few pads of butter to the top of the mixture (don't worry about stirring them in) and then add a few sprigs of fresh thyme to the top of the mixture (don't stir those in, either!)
Bake, covered for 30 minutes.
After 30 minutes, remove the pan from the oven and bump the heat to 180FAN (about 385 Fahrenheit).
Add the frozen peas to the dish and gently press them down into the mixture so they are slightly submerged in the remaining liquid.
Cover and bake for another 10 minutes, and then uncover and finish baking for 10 more minutes, or until the liquid is completely absorbed and the rice is fluffy.