Roast the Vegetables

1. Preheat the Oven: Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper for easy cleanup.
2. Prepare the Vegetables: Spread the chopped broccoli florets, diced potato, chopped onion, and garlic cloves on the baking sheet. Drizzle with olive oil, and sprinkle with salt, pepper, and red pepper flakes (if using). Toss everything together to coat evenly.
3. Roast the Vegetables: Roast the vegetables in the preheated oven for 20-25 minutes, or until the broccoli is slightly crispy and the potatoes are fork-tender, with a little caramelization on the edges. Stir halfway through for even roasting.

Blend the Soup

1. Transfer to a Pot: After roasting, transfer the vegetables to a large pot. Add the vegetable broth and bring to a simmer over medium heat.
2. Simmer: Let the mixture simmer for 10 minutes to allow the flavors to meld together.
3. Blend: Use an immersion blender to blend the soup directly in the pot, or transfer the mixture to a blender in batches. Blend until smooth and creamy. If the soup is too thick, you can add a little extra broth or milk to reach your desired consistency.
4. Season: Taste and adjust the seasoning with additional salt, pepper, or lemon juice if desired.

Finish the Soup

1. Add Milk: Stir in the milk (or dairy-free milk) to make the soup extra creamy. If you prefer a thinner soup, add more broth or milk to achieve your desired consistency.
2. Warm Through: Heat the soup over low heat for a few minutes to ensure it’s nice and hot before serving.