Reheat saucepan over medium low heat and add 1 Tbsp olive oil. Add the garlic and cook until fragrant, then add onion and celery and cook until soft and translucent. Add the apples and herbs and continue to cook, stirring until the apples soften. Add the spinach and a pinch of salt and pepper and cook, stirring, until the spinach wilts. Stir in cooked sausage.