Gourmet beef jerky? This stuff is usually considered a guilty pleasure, if a pleasure at all. It might be better regarded as a compulsion, a weakness like salty potato chips and smoky coffee that overcomes people on long road trips. But take Grand Boulevard south almost to Meramec, and look on the west side of the street for the unassuming storefront of Banh Mi So, a.k.a. Number One Sandwich. The owners, Lynne and Thomas, will buzz you in, and while they prepare your spring rolls, pork meatball sandwich, shrimp soup and iced coffee, let your eyes rest on the little zip-lock bags of treats in the glass display case. Inside them you will see textured brown rectangles that look to be brushed with red stardust. Ask for one to munch while you wait, and you will go where no trucker chawing on a Slim Jim has gone before. The texture is closer to steak than to leather, and the flavor is peppery and sweet. Guilt? No. Pleasure? Oh yes, and perhaps compulsion as you proceed to buy every bag of this homemade Vietnamese delicacy.