Preheat your oven to 400°F.
In a large bowl, toss together the cauliflower and broccoli with olive oil, dried thyme, and dried rosemary.
Arrange the vegetables in a single layer on a large baking sheet.
Roast in the oven for 20-25 minutes, or until the vegetables are tender and lightly browned.
In a large pot, heat a tablespoon of olive oil over medium heat.
Add the diced onions and minced garlic, and sauté until the onion is translucent and fragrant.
Once the onion and garlic are cooked through, add the roasted vegetables to the pot.
Pour in the vegetable broth, and bring the mixture to a boil over medium-high heat.
Reduce the heat to low, cover the pot, and let the vegetables simmer for 20 minutes.
Remove the pot from the heat, and let it cool for a few minutes.
Use an immersion blender to puree the soup until it is smooth and creamy.
If you don't have an immersion blender, you can transfer the soup to a blender and puree it in batches.
Return the pot to the stove over low heat.
Stir in the heavy cream and shredded cheddar cheese, and continue to cook the soup until the cheese is melted and the soup is heated through.
Season with salt and pepper to taste.
Ladle the soup into bowls and serve hot.
Optional: garnish with chopped fresh parsley or chives.
This cauliflower and broccoli cheese soup is a delicious and nutritious meal that is perfect for a chilly day. The roasted vegetables add depth of flavor and a slight sweetness to the soup, and the melted cheese makes it creamy and decadent. Serve it as a main dish or a side, and enjoy!