Preheat your oven to 400°F (200°C). Arrange the diced potatoes, halved onion, and garlic head on a parchment-lined baking sheet. Drizzle generously with olive oil and sprinkle with salt, pepper, thyme, and rosemary.
Roast in the oven for 30 minutes. Then, carefully remove from the oven, cover with foil, and return to bake for an additional 15-25 minutes or until the potatoes are tender and the garlic cloves are soft and golden.
Once roasted to perfection, transfer the vegetables to a large pot. Squeeze the roasted garlic cloves out of their skins and add them to the pot.
Pour in the chicken or vegetable broth and heavy cream. Use a hand blender to blend the mixture until it becomes smooth and creamy. Alternatively, transfer the mixture to a food processor or blender, blend until smooth, then return it to the pot.
Taste the soup and season with salt and pepper to your liking. Warm the soup gently on the stove over medium heat.
When ready to serve, ladle the roasted garlic soup into individual bowls. Garnish with a drizzle of olive oil, chopped parsley, dill, or chili flakes. Pair it with a fresh baguette for a delightful meal. Enjoy every comforting spoonful!