This isn't entirely from scratch, but it beats buying expensive gingerbread houses. I may still try to make a gingerbread houses from scratch, but I haven't had time to figure it out yet. In the meantime, here's our family's attempt at making our own graham cracker houses. I used leftover buttercream icing made from this recipe:
1/2 cup shortening
1/2 cup softened butter
4 cups icing sugar
2 tbsp milk
1 tsp vanilla*
*I used the scrapings of one vanilla bean.
Mix well. Add milk if needed until desired consistency.
(As you browse through the pictures, try to guess where the engineer is. It shouldn't be too hard.)