In a medium saucepan, heat milk, vanilla bean, and seed scrapings. Bring to a gentle boil, cover, and remove from heat. Steep for 30 minutes.
Combine egg yolks and sugar in the bowl of an electric mixer fitted with the whisk attachment. Beat at medium-high speed until very thick and pale yellow, 3 to 5 minutes. Meanwhile, return milk to a simmer.
Remove vanilla bean from hot milk. Add half the milk to egg-yolk mixture, and whisk until blended. Stir into remaining milk, and cook over low heat, stirring constantly, until mixture is thick enough to coat a spoon.
Remove from heat, and immediately stir in cream. Pass mixture through a strainer into a medium bowl, set over an ice bath so that it begins to chill. Stir in vanilla extract, then freeze in an ice-cream maker, following manufacturer's instructions.
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