Combine cheese, flour, salt, pepper, and butter; mix well. Set aside.
Make a lengthwise slit in each date and stuff with a pecan half. Press about 2 teaspoons cheese mixture around each date, covering completely. Chill at least 30 minutes.
Remove dates from refrigerator, and brush with egg white. Place on lightly greased baking sheets. Bake at 350° for 25 minutes. Remove dates to a wire rack; cool completely. Sprinkle with powdered sugar, if desired.