French Onion Stuffed Chicken Casserole

1 tbsp rice bran oil
4 boneless, skinless chicken breasts
2 tsp garlic powder
1 tsp ground thyme
1 cup shredded mozzarella cheese
4 tbsp grated parmesan cheese
2 tbsp butter
4 large onions halved & thinly sliced
SIDS SALT & PEPPER to taste
2 tsp fresh chopped thyme divided
2 tbsp white wine
2 cloves garlic minced
½ cup beef stock, divided

Preheat oven to 200°C.
Lightly grease a 22x30 cm baking dish. Set aside.
Melt butter in a large frypan over medium-high heat. Add onions and season with SIDS SALT & PEPPER and half of the chopped thyme. Cook for 5-8 minutes until soft.
Reduce heat to medium and cook, while stirring occasionally, until onions are caramelized and jammy (about 15 minutes). Pour in ¼ cup of stock if pan gets too dry and keep stirring until onions are browned.
OPTIONAL: Pour in white wine to deglaze the pan and get some additional flavours into the onions. Let cook for a minute until the sauce thickens slightly.
Stir in garlic and cook until fragrant, about 1 minute. Turn off heat and let cool slightly.
Cut chicken breasts in half horizontally to create pockets. Season chicken all over and inside pockets with SIDS SALT & PEPPER, garlic powder and thyme.
Spoon 1-2 tablespoons of caramelized onions into each pocket. Stuff each breast with the cheeses and seal chicken with toothpicks.
Transfer the remaining caramelized onions from the frypan to the prepared baking dish. Mix in remaining ¼ cup of stock then set aside.
Heat oil in the same frypan over medium high heat. Sear the stuffed chicken breasts for 4 minutes each side until browned. (They will not be fully cooked. You will finish them off in the oven.)
Arrange chicken on the caramelized onions in the baking dish. Spoon some of the sauce in the dish over each chicken breast. Top with remaining chopped thyme and bake for 15-20 minutes until fully cooked.
Discard toothpicks. Serve with pan juices and onions.