For the lemon honey chips, toast coriander seeds and crack. Set aside to cool. Slice lemons into 1/8 inch rounds; discard ends and all seeds. Layer lemon slices with cooled coriander in a freezer Ziploc bag or Tupperware container, and pour honey over. Allow the lemons to macerate for a minimum of six hours and up to 24 hours. Strain honey liquid off of slices and reserve.
For the vichyssoise, heat butter and olive oil in a large saucepan. Sweat leeks and onions (3-4 minutes). Add potato slices and cook for 6-8 minutes longer, then add stock, bay leaf and thyme. Cook covered until potatoes are tender through. Remove thyme and bay leaf; allow soup base to cool slightly. Purée until smooth in a blender and then pass through a medium sieve. Completely chill soup, then add crème fraiche, half and half and seasoning. Thin with reserved stock and adjust acidity with the Meyer lemon juice. Reserve chilled.
To make the scallop tartare, combine all ingredients in a chilled non-reactive bowl; reserve chilled. Tartare should be mixed no more than 30 minutes prior to serving.
To plate, refrigerate six small plates or bowls. Chill the soup once more over ice and check again for seasoning; spoon onto plates. Quenelle scallop tartare and gently set in the center of the vichyssoise. Garnish with the fava blossoms, nasturtium and toasted hazelnut. Top with the Meyer lemon chip.