OREO Spread: Beat butter and 2 oz. powdered sugar with electric mixer fitted with paddle attachment until light and fluffy, scraping side of bowl occasionally. Beat in egg until well blended. Add sifted dry ingredients all at once, mixing until combined. Set aside.
Vanilla Syrup: Bring water and granulated sugar to boil in heavy saucepan on medium heat, stirring frequently. Remove from heat; cool slightly. Stir in vanilla. Pour into a wide shallow bowl.
Brioche Toast: Dip each bread slice into Vanilla Syrup; drain slightly. Place onto parchment paper-lined sheet pan. Spread 1 oz. OREO Spread evenly onto each slice. Dust evenly with remaining 0.25 oz. powdered sugar.
Bake in 350°F standard oven 10 to 12 min. or until tops are golden brown at edge and have slight cracks in them. Cool 5 min. before serving.