Heat the grapeseed oil in a large saucepan over medium heat. Add the onion, leek, celery, garlic, and 1 teaspoon salt. Cook, stirring, for 6 minutes, until tender but not colored. Add the potato, the remaining asparagus stems, and the chicken stock. Simmer for 8 minutes, or until the potatoes are tender. Add the cream and simmer for an additional 5 minutes. Transfer the mixture to a blender and puree until smooth. Pass through a fine-meshed sieve into a bowl set over ice. Chill, then season with salt, pepper, and the lemon juice. Reserve, chilled.