Preparation

Make the panna cotta

• In a small bowl, sprinkle the gelatin over 1/2 cup of the cream. Let stand until softened, about 5 minutes.
• Bring the remaining 1/2 cup cream, the sugar, and vanilla to a simmer in a saucepan over medium-high heat, whisking to dissolve the sugar. Remove from the heat and let cool for 1 minute, then whisk in the cream-gelatin mixture until the gelatin dissolves. Stir in the buttermilk.
• Strain the mixture through a fine-mesh strainer into a large measuring cup. Divide the mixture among six 4-ounce ramekins or pour into a small serving bowl. Cover with plastic wrap and refrigerate for at least 5 hours, until set.

Make the compote

• Preheat the oven to 325°F.
• Combine the sugar and 1/2 cup water in a small saucepan and bring to a boil, stirring to dissolve the sugar. Remove from the heat.
• Combine the rhubarb and sugar syrup in a 9-x-13-inch baking dish. Bake, uncovered, until the rhubarb is tender, about 15 minutes.
• Add the strawberries, stir, and bake for 5 minutes longer, until the strawberries have softened. Let cool to room temperature, then refrigerate until ready to use.

To serve

• Run a sharp knife around the edges of the ramekins and unmold the panna cotta onto plates, or serve it right in the ramekins or scoop out of the bowl. Top with the fruit compote.

Make Ahead Tips

Well-wrapped, the panna cotta will keep for up to 3 days in the refrigerator. Top with the compote just before serving.

The compote will keep, covered and refrigerated, for up to 1 week.