1. Preheat your oven to 400 F (200 C). Peel and quarter your mixed onions. If they are very large, you can cut them into sixths or eighths to ensure even cooking. Arrange them in a single layer on a large baking sheet.

2. In a small bowl, whisk together 2 tablespoons of olive oil, maple syrup, Dijon mustard, apple cider vinegar, dried thyme, 1/2 teaspoon salt, and 1/4 teaspoon black pepper until well combined.

3. Pour the maple Dijon mixture over the quartered onions on the baking sheet. Toss gently with your hands or a spatula to ensure all the onions are evenly coated. Spread them back into a single layer.

4. Place the baking sheet in the preheated oven and roast for 25-30 minutes, or until the onions are tender and slightly caramelized at the edges. Give them a stir halfway through cooking to promote even browning.

5. While the onions are roasting, heat the remaining 2 tablespoons of olive oil in a small skillet over medium heat. Add the thinly sliced shallot rings and cook, stirring frequently, for 5-8 minutes, or until they are golden brown and crispy. Watch them carefully as they can burn quickly. Remove them from the pan with a slotted spoon and place them on a paper towel-lined plate to drain any excess oil. Season lightly with a pinch of salt.

6. Once the onions are tender and slightly browned, remove them from the oven. Transfer them to a serving dish and generously sprinkle the crispy shallots over the top. Serve warm.