From The Kitchen Of Erin French
1/4 cup olive oil
1 pound white, yellow or sweet onions, sliced thin
Salt and pepper
2 pounds sunchokes, peeled
1 garlic clove
2 bay leaves
4 sprigs of fresh thyme
4 tablespoons (1/2 stick) unsalted butter
1 1/2 cups half-and-half
1 cup heavy cream
1/2 teaspoon grated nutmeg
1/4 cup créme fraîche
Marigold petals, for garnish (optional)
Dill fronds, for garnish
Heat 2 tablespoons of the olive oil in a large skillet, preferably cast iron, over medium-low heat, toss in the onions and a sprinkle of salt, and cook over low heat, stirring occasionally, until the onions are deeply caramelized, 30 to 45 minutes.
Meanwhile, put the sunchokes in a 4-quart pot, cover with cold water, and add the garlic, bay leaves, thyme, and 2 tablespoons salt. Bring to a boil over high heat, then reduce the heat and simmer the sunchokes until tender and easily pierced with a fork, 12 to 15 minutes.
Drain the sunchokes, discarding the aromatics, and add to the onions. Puree the sunchokes and onions in a blender, working in batches if needed, while still hot. Add the butter, remaining 2 tablespoons olive oil, the half-and-half, cream, and nutmeg and season with salt and pepper to taste. Pulse to blend.
Strain the soup through a fine-mesh sieve into a medium pot. Reheat gently without boiling. Ladle the soup into 4 shallow bowls and top each with a dollop of créme fraîche and a sprinkling of marigold petals, if using, and dill fronds.