Preheat oven to 300°. Coat bottom and sides of an 8-inch springform pan with cooking spray.
Microwave chocolate morsels in a small microwave-safe bowl at MEDIUM (50% power) for 1 minute or until melted and smooth, stirring at 30-second intervals.
Beat butter and 1/2 cup granulated sugar at medium speed with an electric mixer until well blended (about 2 minutes). Add vanilla and egg; beat 1 minute. Add milk and, if desired, bourbon; beat 1 minute. (Mixture will look curdled.) Add melted chocolate, beating just until blended. Gradually add cocoa and flour, beating at low speed just until blended.
Beat egg whites and cream of tartar at high speed with an electric mixer until foamy. Add remaining 1/4 cup granulated sugar, 1 Tbsp. at a time, beating until stiff peaks form. Fold one-fourth of egg white mixture into batter; gently fold in remaining egg white mixture. Spoon batter into prepared pan.
Bake at 300° for 45 minutes or until set. (A wooden pick inserted in center will come out with just a few crumbs on it.) Remove torte from oven; immediately run tip of a small knife around edge of torte. Let cool on wire rack 30 minutes. (Torte will rise to top of pan while baking but will sink while it cools.) Remove sides of springform pan.
Spoon whipped topping into a zip-top plastic freezer bag. (Do not seal.) Snip 1 corner of bag to make a small hole. Pipe dollops of whipped topping around base of torte. Sprinkle torte with powdered sugar and cocoa.
Note: For testing purposes only, we used Hershey's Special Dark Chocolate Chips.