Pre-heat a large dutch oven or soup pan over medium high heat. Add the butter and onions and cook until onions are soft (about 5-7 minutes). The onions and butter shouldn't brown.
Add the minced garlic and stir until fragrant (30 seconds - 1 minute).
Add the broth, carrots, 2 tablespoons of ginger, cumin and red pepper flakes (if using) and stir to combine. Cover and bring to a boil.
Reduce the heat and simmer until the carrots are tender when pierced (approx. 20-25 min). Remove from the heat.
Purée the soup with an immersion blender. If you don't have an immersion blender, use a blender working carefully in small batches. Transfer the soup into the blender and purée until completely smooth. The soup will be HOT so only fill the blender halfway and keep a hand on the top to avoid hot liquid spurting out.
Return to the pan and stir in the whipping cream. Taste and adjust seasonings (ginger, salt, pepper) as needed.
Serve immediately or refrigerate for up to 5 days.