Preheat oven to 400°F (200°C).
In a large oven-safe skillet, melt 2 tablespoons of butter with 1 tablespoon of olive oil over medium-low heat. Add sliced onions and a pinch of salt. Cook, stirring occasionally, for 25-30 minutes until onions are deep golden brown. Remove onions from skillet and set aside.
Pat pork chops dry with paper towels and season both sides with salt, pepper, and thyme.
Increase skillet heat to medium-high and add remaining olive oil. Sear pork chops for 2-3 minutes per side until browned. Remove from heat.
In a small bowl, combine remaining 2 tablespoons of butter with minced garlic.
Return onions to the skillet, placing them over and around the pork chops. Top each chop with a portion of the garlic butter.
Pour chicken stock into the bottom of the pan to prevent burning and maintain moisture.
Transfer skillet to the oven and bake for 12-15 minutes, or until the internal temperature reaches 145°F (63°C).
Remove from oven and let the meat rest for 5 minutes before serving.