In a large pot over medium heat, heat a splash of oil and add the sliced shallots and leeks. Sauté them for about 5-7 minutes or until golden brown.

Preheat your oven to 400°F (200°C). Cut the acorn squash in half, remove seeds, and place it cut-side down on a baking sheet. Roast for 25-30 minutes until tender.

Add the peeled and cubed parsnips along with the roasted acorn squash and hazelnuts to the pot with the sautéed aromatics. Stir to combine.

Pour enough milk and vegetable broth into the pot to cover the veggies. Season generously. Bring to a simmer, then reduce to low and cook for about 15-20 minutes.

Use an immersion blender to blend the soup until creamy and smooth. Blend partially for a chunkier texture if desired.

Serve hot, garnished with toasted hazelnuts and a sprinkle of fresh rosemary.