Remove white papery skin from garlic head (do not peel or separate cloves). Rub 1/2 teaspoon olive oil over garlic head, and wrap in aluminum foil. Bake garlic head at 400° for 45 minutes; let cool 10 minutes. Separate garlic cloves; peel 4 cloves, and reserve for garnish. Squeeze remaining cloves to extract garlic pulp; discard skins.
Combine garlic pulp, 1 cup Vegetable Nage, vinegar, pepper, and salt in a blender, and process until smooth. With blender on, add 2 teaspoons olive oil, and process until well-blended; pour into a small saucepan, and cook over low heat until warm. Set the garlic nage aside, and keep warm.
Combine remaining 1 cup Vegetable Nage, onion, and the next 5 ingredients (onion through bay leaf) in a large skillet; bring to a simmer. Add fish; cover, reduce heat, and simmer 4 minutes or until fish is opaque in color.
Place fish in individual shallow bowls; discard poaching liquid, vegetables, and herbs. Drizzle 1/4 cup warm garlic nage over each fillet; sprinkle with 1 teaspoon shallots, and garnish with a peeled garlic clove.
Shortcut: Substitute 1 cup canned vegetable broth and 1 cup Chardonnay or other dry white wine for the Vegetable Nage, if desired.