In heavy saucepan, stir milk and cornstarch with whisk until cornstarch is dissolved. Stir in 3 egg yolks and 3/4 cup of the sugar. Cook over medium-low heat 8 to 10 minutes, stirring constantly, until mixture begins to bubble and is thick enough to hold soft peaks. Remove from heat; stir in pineapple, 1 tablespoon butter and the vanilla. Spoon into crust.