Combine the garlic, mustard seed, fennel, coriander, ginger, and 1 tablespoon of water in a large dutch oven or pot over medium heat. Simmer for 5 minutes or until the spices are fragrant but not burning.

Chop the leeks into 1/2-inch rounds and add to the pot. Cook for 5 minutes to soften. The garlic should also be browning but not burning.

Add the cauliflower and 6 cups of water. Bring to a boil, then reduce to a simmer and cover. Cook for 20 minutes, or until the cauliflower is soft. Ten minutes before the end, add the beans.

Remove the pot from heat. Add the nutritional yeast, and stir to combine. Blend with an immersion blender, or wait until cooled to room temperature to blend in a blender or food processor.

Divide soup into bowls. Add generous tablespoons of the fresh herbs and salt and pepper to taste.