Warm cauliflower and stock in a saucepan for 5-7 minutes or until cauliflower begins to break down. Transfer to a blender or food processor. Put pot back on stove.
Melt coconut oil over medium heat. Add onion, saute 5 minutes. Add garlic, 30-60 seconds. Transfer to the blender.
Blend mixture one minute on high or until smooth. Salt to taste before adding remaining ingredients. Blend for an additional 30 seconds. Increase wasabi/ horseradish to taste.