For the simple syrup
1 1/4 cups sugar
1 cup water
For the nectarines
6 large nectarines
1/2 cup heavy cream
2 cups Moscato d’Asti
1 tablespoon sour cream
2 teaspoons sugar
1/4 cup hazelnuts, toasted, skinned and coarsely chopped
For the simple syrup: In a small saucepan, stir together the sugar and the water. Bring to a boil, stirring until the sugar dissolves, about 1 minute. (This makes about 1 1/2 cups of simple syrup; you’ll need 1/4 cup for the nectarines. The rest of the syrup may be stored in the refrigerator for at least 2 weeks.)
For the nectarines: For each nectarine, slice off the top and insert a paring knife against the pit. Gently carve around the pit, loosening it from the flesh. Press the knife against the bottom side of the pit and gently push it up and out of the nectarine. (But don’t worry if the bottom of the nectarine gets pulled out with the pit; the cream is thick enough not to leak.)
In a large mixing bowl, combine the Moscato d’Asti and 1/4 cup of the simple syrup. Place the nectarines in the liquid and marinate for 1 hour or more.
When the nectarines are nearly ready, in a medium mixing bowl, whip the heavy cream until soft peaks form. Fold in the sour cream, sugar and chopped hazelnuts.
When ready to serve, remove the nectarines from the marinating liquid. Shave 1/8 inch off the bottoms of the nectarines so that they sit flat. Place each nectarine on a plate. Fill the nectarines with the hazelnut cream. Serve immediately.
The nectarines can marinate in the Moscato d’Asti for several hours. Fill them with the cream just before serving.