1. In a medium pot, heat 2 tbsp. of the olive oil over medium heat. Add onion, carrot, and celery and cook until vegetables just start to soften. Add garlic and cook an additional minute.
2. To the same pot, add lentils, vegetable stock, and crushed tomatoes. Bring to a simmer and cook for 8-10 minutes, or until lentils are soft but not mushy. Add spinach and stir briefly to wilt. Season to taste and reserve.
3. In a sauté pan, heat the additional 2 tbsp. olive oil over medium heat. Add bratwurst and cook on all sides until well browned and at an internal temperature of 145 degrees. Remove and reserve.
4. To Serve: In a shallow bowl, place cooked lentils followed by the bratwurst. Top with the giardiniera and garnish with fresh parsley.