1. Preheat your oven to 350F (175C) for the croutons.

Cauliflower soup:

1. Heat a large pot over medium-high heat and add the oil and butter. 
2. Add the chopped yellow onion, chopped leek, caraway seeds (if using), and sea salt. Cook for 5-7 minutes stirring frequently.
3. Add the diced potatoes, cauliflower florets, bay leaves, and cover with broth/water. Cover and bring to a boil. Lower the heat to medium-low and simmer partially covered for 45-50 minutes.
4. When the potatoes are easily pierced with a fork, take off the heat and take out the bay leaves.
5. Use an immersion blender to blend the soup until creamy or let it cool down slightly and use a blender. Be extremely careful when blending hot soup as the steam could make the blender literally explode (the lid would fly off, see notes).
6. Return pureed soup back to the pot and stir in freshly squeezed lemon juice. Adjust salt and pepper to taste.
7. Serve hot with croutons, a light drizzle of olive oil, and red pepper flakes if desired.

Garlicky croutons:

1. While the soup is cooking, make the croutons.
2. Dice or tear apart the slices of bread, add them to a baking sheet and drizzle with olive oil.
3. Season with salt, pepper, and garlic powder. Toss and bake in the oven for 10-15 minutes. Toss halfway through and keep an eye on them. They should be golden brown and crunchy.
4. Set aside until ready to serve.