Place egg whites in a small bowl; let stand at room temperature for 30 minutes. Meanwhile, using a pencil, draw an 8-in. circle on each of seven sheets of parchment paper. Place each sheet, pencil mark down, on a baking sheet; set aside.
In a large bowl, beat egg yolks on high speed for 5 minutes or until thick and lemon-colored. Gradually beat in sugar. Sift flour twice; gradually add to yolk mixture and mix well (batter will be very thick).
With clean beaters, beat egg whites on medium until soft peaks form. Gradually fold into batter. Place 1/2 cup batter on one of the prepared baking sheets; using a small spatula, spread batter evenly into an 8-in. circle. Bake at 350° for 6-7 minutes or until cake springs back when lightly touched (do not overbake).
Cool on a wire for 5 minutes; gently peel off parchment paper. Repeat with remaining batter and pans. When cool, stack cakes with waxed paper or paper towels in between. Gently smooth top and sides of stack. Refrigerate overnight if desired.
For buttercream, in a small saucepan, melt chips with coffee and sugar; stir until smooth. Remove from the heat. Add a small amount of mixture to egg yolks; return all to the pan, stirring constantly. Cook for 2 minutes or until mixture is thickened and reaches 160°, stirring constantly. Remove from the heat; stir in vanilla. Cool to room temperature.
In a large bowl with a whisk attachment, beat butter until fluffy, about 5 minutes. Gradually beat in chocolate mixture. If necessary, refrigerate until frosting achieves spreading consistency.
Set aside one cake layer. Spread 1/4 cup frosting on each of the remaining cake layers; stack on a serving plate.
In a small saucepan, melt caramels with milk. Remove from the heat; pour evenly over reserved cake layer. Place on top of cake. Frost sides of cake and decorate the top with remaining frosting.