Preheat oven to 375°F. In a medium bowl, use an electric mixer to beat cream cheese, powdered sugar, vanilla, and strawberry jam until smooth and creamy.
Unroll crescent roll dough and separate into four rectangles. Press firmly along the triangle perforations to seal. Place rectangles on an ungreased baking sheet (or a baking sheet lined with parchment paper).
Divide cream cheese mixture evenly between the four pieces of dough, spreading on one half of each rectangle and leaving a thin border around the edges. Arrange strawberry slices on top of cream cheese mixture, using about 1 ½ strawberries per pastry (or whatever fits).
Fold dough over filling so that edges meet, and press along edges firmly with a fork to seal. Brush top of each pastry with milk and sprinkle with sugar. Using a sharp knife, cut three diagonal slits on surface of each pastry.
Bake for 13 to 16 minutes or until pastries are a deep golden brown. Place pan on a wire rack and cool pastries for 10 minutes before removing with a spatula and serving warm.
You may easily double this recipe to yield 8 pastries.