How to Make It
Bring a medium saucepan of water to a boil and fill a bowl with ice water. Add the edamame to the boiling water and cook until tender, about 5 minutes. Using a slotted spoon, transfer the edamame to a plate and pat dry.
Cook the pearl onions in the saucepan of boiling water for 3 minutes. Drain the onions and transfer them to the bowl of ice water to cool completely. Using a paring knife, trim off the root ends and peel the onions and pat dry.
Melt the 1/2 tablespoon of butter in a medium deep skillet. Add the peeled onions and the sugar and cook over moderately low heat, stirring, until lightly browned, about 15 minutes. Add the heavy cream and thyme and simmer until slightly reduced, about 5 minutes. Add the edamame and Turkey Stock and bring to a boil. Season with salt and pepper. Stir the cornstarch slurry, then add it to the cream sauce and cook, stirring, until thickened, about 2 minutes.
Preheat the broiler and set a rack 6 to 8 inches from the heat. Pour the edamame mixture into a 2-quart shallow baking dish. In a small bowl, mix the 1 tablespoon of melted butter with the panko. Sprinkle the crumbs over the edamame and broil for about 3 minutes, or until golden and bubbling; serve hot.