2 sweet potatoes or 1 yam, peeled and cut into 1-inch chunks
1 tablespoon molasses
1 tablespoon honey
1/2 teaspoon vanilla extract
2 teaspoons brown sugar
1/4 teaspoon ground nutmeg
1/2 teaspoon ground cinnamon
1 quart heavy cream
2 vanilla beans, split and seeds scraped
1 cup sugar (1/2 cup and 1/2 cup measured separately)
6 egg yolks
1 tablespoon butter