PREHEAT oven to 400°F. Mix cream cheese, 1/4 cup of the sugar, vanilla and egg yolk with wire whisk until well blended. In separate bowl, mix remaining 1/4 cup sugar and cinnamon; set aside.
FLATTEN each bread slice with rolling pin. Spread 1 side of each slice evenly with 1 rounded Tbsp. cream cheese mixture. Starting at short end, tightly roll up. Brush each roll with butter; roll in reserved cinnamon-sugar. Slice each roll into 3 pieces.
PLACE each piece, seam side down, on baking sheet. Bake 12 to 15 min. or until edges are lightly browned. Serve immediately.