Heat your olive oil in a large pot over medium heat for about a minute. Add the diced onion and cook for 4 minutes until it starts getting soft and translucent. Stir in the minced garlic and let it cook for another minute—you'll smell it right away, which means it's perfect.

Pour in your 4 cups of diced tomatoes (with their juice if using canned) and the vegetable broth. Bring everything to a simmer and let it bubble gently for about 15 minutes. This lets the flavors meld together and the tomatoes break down naturally.

After 15 minutes, take the pot off the heat and let it cool for just 2-3 minutes. Use an immersion blender to puree the soup until it reaches your desired consistency—I like mine totally smooth, but some people prefer it a tiny bit chunky.

Return the pot to low heat and slowly stir in the heavy cream and milk. Keep the heat low here because if it gets too hot, the cream can separate and look weird. Stir constantly for about 3-4 minutes until it's completely blended and creamy.

Taste your tomato basil soup recipe now and adjust the salt and pepper as needed. This is super important because seasoning at the end tastes way better than trying to fix it later. I usually add a pinch more salt because the broth is sometimes on the mild side.

Tear up your fresh basil leaves and stir them in gently, saving a few pieces for garnish. Turn off the heat immediately after adding the basil so it stays bright green and fresh. Don't cook it—just let it wilt into the hot soup.

Ladle the soup into bowls and top with a basil leaf if you saved some. Serve immediately while it's steaming hot. This is when the flavor absolutely shines and you get that perfect creamy texture.