Preheat oven to 200°C.
Heat 1 tbsp of oil in a large ovenproof pan over high heat. Liberally season both sides of the chicken breasts with salt and pepper before transferring to the pan.
Sear the chicken 2-3 minutes per side, just until it develops a golden-brown colour. Remove the chicken from the pan and set aside.
Allow the pan to cool slightly before cooking garlic in remaining tbsp oil over medium heat until fragrant.
Pour in the stock, lemon juice, and oregano and stir until the mixture is smooth. Slowly add yoghurt before mix gets to the boil to prevent curdling.
Let reduce slightly, and add spinach. Allow spinach to wilt slightly.
Place the chicken breasts back into the pan and transfer the pan to the oven. Bake for 15 minutes or until the chicken is fully cooked.
Serve half a breast of chicken on a bed of the wilted spinach and top with a drizzle of the creamy sauce.