Flippin' geniuses, those people.
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In a (futile) attempt to make it a wee bit healthier, I used wheat bread and left out the mayo. The "dipping in egg and frying in butter" probably negated a lot of that.
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The wheat bread probably wasn't firm enough for this, but I was able to de-soggify it with a 15-minute trip to a hot oven.
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Space needed: Minimal.
One plate to build the sandwich, one bowl for the egg, and a frying pan on the stovetop.
Cost: Under $5.
The ingredients for one recipe-specific sandwich come out to about $3.50 (to be exact, $3.46 according to prices here in the DC/Baltimore area). I ended up only needing one slice of cheese for full sandwich coverage, so mine came in at $2.86. That was with Boar's Head meats and Alpine Lace swiss; store brand deli products would have easily knocked this down to less than $2.50.
Recipe: Monte Cubano from Gourmet magazine, March 2009