Cook 1/2 cup maple syrup in a heavy saucepan over medium-high heat until syrup reaches hard ball stage (260°). Pour immediately into 6 (6-ounce) custard cups coated with cooking spray; tip quickly to coat bottom of cups. Set aside.
Place flour in a medium bowl; gradually add remaining 1 cup maple syrup, stirring with a wire whisk until blended. Add milk, vanilla, and eggs; beat at low speed of a mixer until well-blended. Pour evenly into prepared cups; place cups in a 13 x 9-inch baking pan. Add hot water to pan to a depth of 1 inch. Bake at 375° for 1 hour and 10 minutes or until a knife inserted in center comes out clean. Remove cups from water; let cool completely on a wire rack. Cover and chill 2 hours.
To serve, loosen edges of custard with a knife or rubber spatula. Place a dessert plate, upside down, on top of each cup; invert custard cups onto plates. Drizzle any remaining syrup over custard.