Servings: Serves 10–12
- 2 Tbsp. olive oil
- 2 Tbsp. unsalted butter
- 6 cups thinly sliced red or yellow onions (about 3 1/4 pounds)
- 1/2 tsp. red pepper flakes
- 1 cup packed light brown sugar
- 1/4 cup balsamic vinegar
- 1/2 cup dry sherry
- 1/4 tsp. salt
- 1/2 pound chicken livers , rinsed and trimmed
- 1 small onion , coarsely chopped
- 1 small clove garlic , minced
- 1 tsp. fresh thyme leaves
- 1/2 tsp. kosher salt , plus more to taste
- 1/2 tsp. freshly ground pepper , plus more to taste
- 1 bay leaf
- 1 1/2 sticks unsalted butter , at room temperature
- 2 tsp. cognac
- Toasted baguette , for serving
- Mixed greens , for serving
To make marmalade: Heat oil and butter in heavy large pot over medium heat. Add onions and dried red pepper. Cover and cook until onions are tender, stirring occasionally, about 15 minutes. Remove the lid and continue cooking until onions are deep golden brown, about 15 minutes more. Add brown sugar, vinegar, and sherry; stir gently to combine. Cook uncovered, stirring frequently, until onions are very tender and mixture is thick, 30 to 40 minutes. Stir in salt, remove from heat, and cool completely. Transfer to a container and refrigerate (can be refrigerated for up to 2 weeks).
To make crostini: In a medium saucepan, combine chicken livers, onion, garlic, thyme, salt, pepper, and bay leaf. Add 1/2 cup water and bring to a simmer over medium heat. Cover, reduce heat to low, and cook, stirring occasionally, until livers are barely pink inside, about 3 minutes. Remove from heat and let stand, covered, for 5 minutes.
Discard bay leaf. Strain liquids and transfer liver mixture to a food processor; pulse until coarsely pureed. With the machine on, add butter 2 tablespoons at a time, until incorporated. Mix in cognac, and season to taste with salt and pepper if desired (the texture should be nearly smooth). Serve warm on toasted baguette with onion marmalade on top, and with mixed greens on the side.
Note: Instead of spreading the warm chicken liver mixture on the baguette, you can chill and slice it.