Place butter in a large bowl. Beat with a mixer at medium speed until light and fluffy. Combine milk, salt, and egg yolk in a small bowl; stir well with a whisk. Add milk misture to butter, 1 Tbs at a time, beating well after each addition. Add four; beat just until combined. Press mixture into a 4-inch circle on plastic wrap; cover. Chill for 1 hour.
Preheat oven to 350F. Unwrap and place chilled dough on a lightly foured surface. Roll dough into a 10-inch circle. Fit dough into a 9-inch pie plate. Freeze 15 minutes.
Bake at 350F for 25 minutes or until lightly browned. Cool.