Make up some royal icing. Split it up; dye one batch red, another green. (Keep a bunch white.)
Cut your graham crackers to size per the pattern above. I found that using a sharp paring knife that I kept wetting (since graham crackers turn to mush when damp) and a lot of patient, repeated cuts over the same line worked well.
Royal icing turns to goo with a very small amount of water added. Take some of your red and some of your white; add a little bit of water to each. (Not too much, or you’ll soak the graham crackers, and, well, mush.) Spread the color on the cut pieces as above. Leave them to dry a couple hours.
Cut a milk chocolate and a dark chocolate Hershey bar into bricks (4 per rectangle). Glue down the 3 floor graham crackers to the work surface with royal icing. Wet down some more royal icing, adding black food coloring if desired, and spread it out for mortar. Lay down the chocolate bricks, leaving room for the cafe walls to go in.
Once the walls are dry, start gluing the pieces together, as shown above. Use an extra piece of graham cracker propped up with leftover bricks for the bar. Soak some Mike & Ikes in warm water to remove the outer coating. Mix & match to fill the bar with bottles. Wrap the mini LED lights a few times around the ceiling of the first floor to light the interior. Leave some extra light wire trailing off to string up as hanging lights.
Add details: Mint chocolates on leftover bricks for tables. Green tip-frosted plants. Mint planters with green tip-frosting plants on top. More Mike & Ike bottles. Candy cane light posts.