Preheat oven to 400°F (205°C). Grease 2 large baking sheets or line with parchment paper for easy cleanup.

Remove the cauliflower florets and cut into bite-sized pieces. Spread across one baking sheet in a single layer. Slice up the thick stalk and leaves then spread over to the second baking sheet. Drizzle 1 tbsp oil and a good punch of salt and pepper over each tray.

Without removing the individual cloves from the head, peel off the outer-most, papery skin on the garlic head. Use a sharp-knife to cut off about ¼-inch off the top of the garlic head to expose the cloves.

Place the garlic head in a small piece of parchment paper and/or foil and drizzle with oil (about 1 tbsp). Season with salt and pepper. Use your fingers to spread the oil and spice all over the garlic. Wrap the garlic up in the paper/foil so it's completely covered. Place the garlic bundle, seem side down on to the baking sheet with the cauliflower.

Roast garlic and cauliflower for about 30-35 minutes until the cauliflower is tender and the edges have started caramelized and golden. When done roasting, remove from the oven and set aside until needed. Unwrap the garlic and let it cool for about 5-10 minutes until cool enough to handle. To easily remove the peel, pinch from the bottom of the clove and pull up - the garlic should pop right out.

About halfway through roasting the cauliflower, start on the leeks. Heat a large soup pot over a medium heat. Add olive oil to the pot. Once hot, add the sliced leeks, thyme and rosemary. Cook, stirring every so often to soften the leeks.

Add the peeled cloves to the pot along with cauliflower and broth/stock. Stir everything together.

Use an immersion blender to puree the soup until it smooth and creamy. Alternatively, you can transfer the soup to a regular blender or food processor if you don't own an immersion blender. If the soup is too thick, add water and blend. Repeat until it's your preferred consistency.

Taste and season as needed and serve.

Store leftover soup in an airtight container in the fridge for about 5 days.