Chilled Cauliflower Soup with Sea Urchin Roe

In a medium saucepan, melt butter over medium heat. Add onions and cook until tender, stirring to prevent color. Mix in cauliflower and sake, bringing to a simmer. Add chicken stock and simmer, covered, until cauliflower is soft, approximately 30 minutes. When tender, allow to cool slightly and puree in blender until smooth. Strain through a fine-mesh sieve. Season to taste with salt, pepper, and lemon juice. Cool in an ice bath. When chilled, adjust consistency with milk, and again season to taste. Serve chilled soup in a shot glass, top with one piece sea urchin roe, and garnish with shiso blossoms.