Bring oil to medium-high heat in a large (3 1/2 quart) dutch oven. Add fennel and shallot, stirring to coat. Cook for 5 minutes, until vegetables are lightly softened.
Add half of cabbage and salt, stirring and cooking for two minutes to wilt slightly, then add remaining tablespoon of olive oil, cabbage, and brazil nuts.
Continue stirring occasionally and cooking over medium heat for 10 minutes. You should see light browning on the vegetables.
Then add dijon mustard, garlic powder, and 2 1/2 cups stock. Cover and simmer for 20 minutes, on medium-low heat.
Take off heat and gently transfer half of it to a high-powered blender. Add collagen and black pepper.
Blend for 30 seconds, then add other half. Blend for 45 seconds on high to completely puree, adding up to 1/2 cup of stock if needed to get to the texture you like. Taste, and adjust salt if needed.