Preparation

• Position a rack in the center of the oven, and heat the oven to 425°F.
• Use a 1- or 1-1/2-inch-diameter round biscuit or cookie cutter to punch out rounds of the challah; you should have about 24 pieces. Set the rounds on a large rimmed baking sheet. Bake until brown and crisp, about 6 minutes. Remove from the oven, and let cool to room temperature.
• Put the cream cheese, lemon juice, dill, chives, and 1/2 tsp. each salt and pepper into a food processor, and pulse until combined. Season to taste with more salt and pepper.
• Place the challah rounds on a large platter, spread generously with the cream cheese, top with 2 slices of the fennel, and then fold a piece of salmon into a roselike shape and set on top. Sprinkle with the lemon zest and dill sprigs, and serve.