Line a 13x9-in. baking pan with parchment paper, letting end extend over sides by 1 inch.
In a large bowl, cream butter and brown sugar until fluffy. Beat in eggs and vanilla. In another bowl, whisk flour, baking powder and salt; gradually add into creamed mixture. Spread onto bottom of prepared pan.
In a small bowl, mix sugar and cinnamon; sprinkle 2 Tbsp. mixture over batter in pan. Bake in a preheated 350º oven for 25-30 minutes or until edges are light brown. Cool completely in pan on a wire rack.
Spread dulce de leche over crust. In a small saucepan, combine white baking chocolate, cream and corn syrup; cook and stir over low heat until smooth. Cool slightly. Spread over dulce de leche. Sprinkle with remaining cinnamon-sugar and refrigerate, covered, for at least 1 hour.
To serve, remove from pan, lifting with parchment paper. Cut into bars and refrigerate leftovers.
NOTE: This recipe uses Nestle La Lechera dulce de leche, which can be found in the International foods section of your store. You may use Eagle Brand dulce de leche (caramel flavored sauce); thicken it according to package directions before using.