In advance: Make flowers using Flower Making Set. Tint 8 oz. fondant rose and roll out 1/16 in. thick. Cut 285 forget-me-nots; make extras to allow for breakage.
Place on thick foam and cup centers using end of stick 1 which has been dipped in cornstarch. Use royal icing to pipe tip 2 dot centers; let dry.
Add trims in violet royal icing. Ice tower peaks and sprinkle with Cake Sparkles.
Pipe tip 3 arch around windows on towers and main roof; sprinkle with Cake Sparkles. Outline door and windows for cake sides with tip 5; sprinkle with Cake Sparkles. Ice sides of main roof and overpipe scalloped edge with tip 5; sprinkle with Cake Sparkles. Let dry.
Prepare towers to insert in cake. To make 1 large, 4 medium and 2 small towers which will be inserted into cakes more stable, attach plastic dowel rods, cut 1 in. shorter than height of cake, to bottom of towers. Stand tower upside down; attach cut dowel rod to base with melted candy. Refrigerate until firm.
Ice 2-layer cakes smooth. Prepare for Stacked Construction; position 6 in. cake ½ in. from center toward back of 10 in. cake to allow for main roof in front. Working from top to bottom, assemble and decorate using buttercream icing.
Decorate 3 towers (small, medium, large) for 6 in. cake top. Attach tower peaks and flowers under windows; pipe tip 3 dots on battlements and tip 2 double drop strings above windows. Add tip 349 leaves.
Insert first 3 towers into cake top. Pipe tip 5 bead border around tower bases and bottom of 6 in. cake. Attach flowers for top border; add tip 349 leaves. Insert 4 plastic windows around sides of 6 in. cake. Attach flowers under windows; pipe tip 349 leaves. Position main roof on 10 in. cake. Prepare 3 medium towers and 1 small tower as described above. Insert in 10 in. cake and pipe tip 5 bead border around bases and bottom border of 10 in. cake. Attach flowers for top border; add tip 349 leaves. Insert door at front and 2 plastic windows on sides of 10 in. cake. Attach flowers under windows and around door; pipe tip 349 leaves. Prepare 3 large and 2 small towers as described above for sides of cake; attach to cake board, touching cake sides. Pipe tip 12 random zigzag around base; position flowers and pipe tip 349 leaves.