Place 1 meringue layer on a cake stand, and spread 1 1/2 cups buttercream over its surface. Top with a slice of genoise. Brush genoise with one-third of the syrup. Spread 1 1/2 cups buttercream over genoise. Repeat layering 2 more times. Spread enough buttercream over sides of cake to fill in any spaces between layers and create a smooth surface. Refrigerate cake for at least 8 hours (preferably overnight).
Just before serving, spread frosting over cake, smoothing sides and creating peaks on top to resemble snowdrifts. Sprinkle top with sanding sugar. Gently press 3 cookies onto each side of cake, using 1 of each shape per side and alternating molasses and honey gingerbread. Serve immediately.