Panna cotta in Italian literally means "cooked cream." It's basically an eggless custard thickened with gelatin and served cold. Our version adds an infusion of strawberries and orange for a festive and light springtime dessert.
Because gelatin can impart a rubbery texture to desserts, a minimal amount is used here; this allows you to make the dessert a day or two in advance. By the same token, this panna cotta is much slower to set up and needs at least 8 hours in the refrigerator, so plan accordingly.
Combine the strawberries, sugar and orange zest in the bowl of a food processor or blender. Purée until very smooth. Add the buttermilk and purée for 1 minute. Place a fine mesh sieve or chinois over a bowl. Add the purée and press firmly to extract the pulp and seeds. Discard the solids and set the strained purée aside.
Place the Grand Marnier in a small bowl and sprinkle the gelatin over the liqueur. Let sit 5 minutes to soften the gelatin.
Place the 3/4 cup heavy cream in a small pot and bring just to a simmer. Remove the pan from the heat and stir in the gelatin mixture. Add the strawberry-buttermilk purée and whisk to combine.
Divide the panna cotta between 6 martini glasses or wine goblets. Refrigerate until firm, at least 8 hours.
Optional garnish: Whip the remaining 1/2 cup cream with the sugar and crème de menthe until it forms stiff peaks. Pipe or spoon a dollop of the cream atop each panna cotta, and garnish with a sprig of mint.