Are we, or are we not, a nation of sandwich lovers? I would venture that we are probably more obsessed about sandwiches than most any other food, other than perhaps pizza and barbeque. David Schwen, a subversively funny designer, has captured our preoccupation with all that fits between two slices of bread. But he has brilliantly distilled it down to the barest of elements. I think you can buy a print version of a hamburger here. And a tee shirt here. I am going to lunch now…