Bring a large pot of water to a boil. Meanwhile, prepare an ice-water bath, and set aside. Place peaches in boiling water for 1 to 2 minutes; remove with a slotted spoon, and transfer to ice-water bath. Keep the pot of water on the stove. Peel peaches, and cut in half, discarding pits. Reserve ice-water bath.
In a large skillet, melt butter over medium-high heat. Sprinkle 1/4 cup sugar over butter; add peaches, cut side down. Cook until they start to brown, about 4 minutes. Reduce heat to medium; cook until sugar caramelizes, about 6 minutes more, spooning syrup over peaches occasionally. Reduce heat to low, turn peaches, and cook until caramel turns amber in color, about 2 minutes more. Remove pan from heat, and let cool.
Meanwhile, return the pot of water on the stove to a boil. Reduce heat; simmer.
Make sabayon: In the bowl of an electric mixer fitted with the whisk attachment, beat remaining 1/4 cup sugar and egg yolks until pale and thick, about 2 minutes, scraping down sides of the bowl once. Add moscato, and beat for 2 minutes more.
Transfer yolk mixture to a large clean metal bowl, and set over the simmering water. Whisk until the sabayon thickens and is fluffy and slightly stiff, about 3 minutes. Set bowl in ice-water bath. Continue whisking until chilled, about 3 minutes.
Whip cream to medium-stiff peaks; fold into chilled sabayon. At this point, sabayon may be refrigerated for up to 24 hours. To serve, divide among six goblets. Place a peach half on sabayon, and top with 3 generous tablespoons of warm raspberry sauce.