Keto Cauliflower Soup with Rosemary Oil

Rub garlic head with olive oil and cover with foil.  Roast in the oven for 40-50 minutes, till caramelized. Set aside.

How to make the rosemary oil: In a medium skillet, combine the olive oil and rosemary sprigs. Cook over low heat for 5 minutes, lowering the heat if the oil reaches a full simmer (You want to cook it at a very gentle simmer to avoid frying the rosemary). Carefully pour the oil and the rosemary into a small bowl, leaving a slick of oil in the pan if you plan to make croutons. Allow the rosemary to cool completely in the oil while you make the soup.

How to make the soup: In a heavy pot or Dutch oven, heat 2 tablespoons olive oil over medium-low. Add the onion and cook, stirring occasionally, until tender and translucent- about 6 to 8 minutes. Squeeze the head of garlic into the pan, breaking it up with a fork, and cook about 30 seconds.

Add the stock, cauliflower, salt, and pepper, and bring to a boil over high. Lower the heat, cover, and simmer until the cauliflower is tender when pierced with a fork, about 10 minutes.

Meanwhile, make the optional croutons: Heat the reserved skillet with the residual rosemary oil over medium. Add the bread cubes, sprinkle generously with salt and pepper, and cook, tossing often, until toasted all over, 4 to 5 minutes. Transfer the croutons to a plate or board to cool.

Strain and discard the rosemary stems from the rosemary oil. Working in batches if necessary, carefully transfer the vegetables, stock, and 1/4 cup rosemary oil to a blender and blend on high until creamy. Add more rosemary oil to taste, and blend to combine. Return the soup to the pot and bring to a simmer. If the soup seems thin, let it simmer for 5 to 10 minutes to reduce slightly. (Remember: The soup will continue to thicken as it cools.) Season to taste with salt and pepper.

Serve hot. Garnish each serving with a swirl of rosemary oil, a few croutons, and a sprinkle of lemon zest. The soup will thicken as it sits; add more stock as necessary when reheating. Leftover rosemary oil will keep in a sealed container at room temperature for up to 1 week.