Preheat your oven to 400°F if using the roasting method. In an oven-safe dish, combine the halved roma tomatoes, cherry tomatoes, roughly chopped onion, halved head of garlic, extra-virgin olive oil, and a generous pinch of kosher salt and black pepper. Toss everything well to coat. Roast in the oven for 30-40 minutes until the vegetables are tender and the tomatoes are starting to burst and char. Alternatively, you can place all these ingredients in a large pot on the stovetop over medium heat and simmer until the vegetables are soft and tomatoes have burst, stirring occasionally.

While the vegetables are roasting, thinly slice the baguette and arrange the slices on a baking sheet. Drizzle each slice with a little olive oil, then generously cover with shredded gruyère cheese. Season with salt and pepper. Bake in the oven until the cheese is melted and the bread is golden and crispy, about 15 minutes. Set aside the toasts until serving. I like to make extra toasts for dipping — they go fast!

Once the vegetables are roasted and tender, transfer them (including all the juices and oil from the pan) to a high-speed blender. Squeeze the roasted garlic cloves out of their skins into the blender and discard the skins. Add the vegetable or chicken broth and the large basil leaves. Blend everything until smooth. If you prefer a chunky texture, pulse the mixture a few times instead of blending completely smooth.

Pour the blended soup back into a clean pot (if needed) and reheat gently over medium-low. Stir in the heavy cream and balsamic vinegar. Taste and adjust salt, pepper, and add a little sugar if needed to balance acidity. Heat through but do not boil. For a more luxurious texture, I like to add a splash more cream or even swirl some in when serving.

Ladle the hot soup into serving bowls. Top with the crispy gruyère toasts (from Step 2) and garnish with extra fresh basil leaves. Serve right away for the best flavor. I like to serve with a few extra toasts on the side for dipping, and a drizzle of olive oil over the soup for extra richness.