- 1 vanilla bean, split lengthwise
- 1 cup plus 2 tbsp sugar
- 1 tbsp instant coffee
- 1 tbsp boiling water
- 6 large egg yolks
- ¼ cup Marsala
- 1¼ cups heavy cream
- 2/3 cup plain low-fat yogurt
- 1 cup chopped pistachios, plus more for garnish
- Rose petals, for garnish (optional)
- 8 in (20cm) square metal cake pan
- Lightly oil an 8 in (20cm) square metal cake pan and line it with a sheet of plastic wrap. Scrape the seeds from the vanilla bean into a saucepan. Add the sugar and ½ cup water. Stir over medium heat until the sugar dissolves. Boil without stirring about 3 minutes, until syrupy. Dissolve the coffee granules in the boiling water, and stir into the syrup.
- Beat the egg yolks and Marsala in a large bowl with an electric mixer. Beat in the coffee syrup in a steady stream, and beat about 6 minutes, until thick and tripled in volume.
- Whip the cream in a chilled bowl until soft peaks form. Fold into the egg mixture with the yogurt and ¾ cup of the pistachios. Spread the cake pan and sprinkle with the remaining pistachios. Cover with plastic wrap and freeze for 4–5 hours, until firm.
- Invert the pan to unmold the semifreddo onto a chilled platter, remove the plastic wrap, and turn right side up. Cut into squares with a knife dipped in hot water. Serve immediately on chilled dessert plates, sprinkled with more pistachio nuts and rose petals, if using.