Oreo Crumb Crust: Combine ingredients. Press 2.5 oz. mixture onto bottom and up sides of each of 5(5-inch) tart pans with removable bottoms. Place prepared pans on half sheet pan. Bake in preheated 350°F standard oven 8 min. Remove from sheet pan and cool tart pans completely on wire rack.
Caramel Tart filling: Bring cream, corn syrup, butter and salt to boil in heavy saucepan on medium heat; remove from heat.
Meanwhile, caramelize sugar in heavy bottom saucepan on medium-high heat until golden brown; remove from heat. Carefully and slowly add hot cream mixture, stirring constantly, until all cream is incorporated. (Exercise caution in doing this, as steam will rise from the caramel mixture.) Bring mixture back to boil; boil 30 seconds. Remove from heat; add vanilla. Cool to room temperature.
Portion 2.5 oz. Caramel onto bottom of each baked crust. Let stand at room temperature until completely set.
Bittersweet Ganache Filling: Bring cream and salt to boil in heavy saucepan on medium heat. Pour over chocolate. Let stand 1 min. Stir slowly until chocolate is completely melted and mixture is well blended. Cool to 90°F. Portion 2 oz. mixture over caramel in each tart. Refrigerate until ganache is firm.
Soft Ganache: Bring cream to boil in heavy saucepan on medium heat. Pour over chocolate. Whisk until mixture is smooth. Refrigerate until cool.
Oreo Florentines: Melt butter in saucepan on medium-high heat; remove from heat. Stir in remaining ingredients, except OREO Base Cake, until well blended. Drop 5 (0.7-oz.) portions of batter onto parchment paper-lined half sheet pan. Spread each to 1/8-inch thickness. Sprinkle each with 1/4 tsp. OREO Base Cake. (Store remaining Florentine batter up to 1 week in refrigerator for later use.)
Bake in 350°F convection oven 7 to 9 min. or just until tops are set. While still very warm, cut a 4-1/2-inch circle out of each cookie. Then, cut a 3-1/2-inch circle inside of each larger circle to create a ring. Save center portion of cookie for another use. Cut each ring in half to create 2 semi-circles. Cool completely.
For Each Tart: Gently whip Soft Ganache to loosen it up. Spoon into pastry bag fitted with #6 plain tip. Pipe 5 "pearls" of ganache onto each half of the tart, just inside of the edge. Place Florentine semi-circle over each set of pearls. Remove tart from pan; cut in half. Serve 1/2 tart per person.