Savor Soup House PHOTOS: Matt D'Annunzio

What Portland's fast-growing legion of food carts lacks in, say, walls, seats and plumbing, it makes up for in vibrant spice, bargain prices and a double helping of space-saving ingenuity. What makes these pint-sized operations special is often their allegiance to a single dish, from waffles to noodles to Belgian frites. Here are four carts that do their obsessions proud.

There's your mom's grilled cheese sandwiches and then there are Nancy Ettinger's grilled cheese sandwiches—thick, crusty slabs of Grand Central slathered with butter and stuffed with everything from Gruyère and Tillamook cheddar to caramelized onions, truffle oil and apple butter. Plus, a rotating cast of hearty guest-star soups—posole, tomato with fennel, butternut squash stew—that turn every day into the best day ever.

1003 SW Alder St., 750-5634. 11 am-3 pm Monday-Friday.

Rice and chicken—what could be simpler? But the heady flavors of garlic, ginger and chiles Thai emigrant "Nong" Poon Sukwattana Narumol packs in and on her tender, boiled chicken are legendary. Big, butcher-paper packets of the hearty dish with a side of thin Chinese winter squash soup are all she sells alongside Vietnamese coffee and a few funky juices. And, really, it's all you need.

Southwest Alder Street in between 10th and 11th avenues, 971-255-3480, 10 am-4 pm or “sold out,” Monday-Friday.

This egg-centric breakfast cart is barely open past noon, but after plowing through one of its compact sandwiches (and a french press of Ristretto), you won't need to eat for the rest of the day. I've already sacrificed my left ventricle to the Mississippi Monte Cristo, a so-wrong-it's-right stack of grilled ham, eggs and salty Gorgonzola drizzled with maple syrup, sandwiched between two crunchy slabs of vanilla-cardamom brioche french toast.

4233 N Mississippi Ave., 7 am-2 pm Monday, Wednesday-Friday, 9 am-1 pm Saturday-Sunday.

Jesse Sandoval may be the former drummer for the Shins, but at heart he's a wrinkled grandma stirring a pot of lip-tingling posole on the side of the road of some New Mexican high desert. Or at least, that's how I imagine him as I devour a midget-sized red chile chicken burrito or a puffy, fried-to-order, beef- and tart-green-chile-stuffed sopapilla—quenching the burn with a swig of Mexican cane-sugar Coke. Thanks, Grandma.

4233 N Mississippi Ave. Lunch and dinner Wednesday-Sunday.