Step 1

Place 1/4 cup cold water in a small bowl. Sprinkle gelatin over; let stand 10 minutes.

Step 2

Heat 1/2 cup cream in a medium saucepan over medium heat until very warm (it will deactivate the gelatin if it gets too hot). Remove from heat, add gelatin and 2/3 cup sugar, and whisk until they are completely dissolved. Gradually stir in remaining 2 1/4 cups cream, then buttermilk. Divide among eight small bowls or 6-ounce ramekins and chill until set, at least 4 hours.

Step 3

Meanwhile, bring apricots, 2 tablespoons sugar, and 1 cup water to a boil in a small saucepan, reduce heat, and simmer, stirring occasionally, until thickened and jam-like, 20–25 minutes. Let compote cool completely.

Step 4

Bring remaining 1 tablespoon sugar and 2 tablespoons water to a boil in a small saucepan over medium-high heat and cook, swirling often, until thick and syrupy (do not let it take on any color), about 4 minutes. Add fennel seeds and reduce heat to medium. Cook, stirring constantly, until sugar starts to become dry and crystallized, about 2 minutes. Remove from heat and stir until sugar is completely dry and crystallized, about 1 minute longer. Transfer seeds to a small bowl; set aside.

Step 5

Serve panna cotta topped with compote and candied fennel seeds.

Step 6

DO AHEAD: Panna cotta can be made 3 days ahead; cover and keep chilled. Compote can be made 1 week ahead; cover and chill.