In Hawaii they cook whole hogs underground with hot rocks and banana leaves. It's called Kalua Pig and it is Amazing. I set out to replicate this delicious and wonderful pork on a smaller scale in my backyard without having to dig a big ol' hole and cook an entire pig. In the process I built a dual purpose grill and hot rock BBQ.
The cooker is built from 2 dozen cinderblocks, dirt, rocks and a few other materials that you probably have on hand. With this inexpensive setup you will be able to have a two day Meatfest starting with your favorite grilled vittles and culminating in amazing Kalua pork.
Here is the disclaimer: This cooker involves heating rocks to a dangerous temperature and then covering them with potentially flammable vegetation and then leaving it unattended for many hours. If you are careless or unlucky you might burn up.
To build the cooker you will need:
24 CINDERBLOCKS - these cost me $30. This was the only thing I had to buy other than the pork.
1 STEEL OR IRON GRATE - must fit over the cooker. I borrowed one from a weber, but i didn't quite fit and I had to use a pipe to stabilize it. I bet an oven rack would be perfect!
DIRT - cheap! suitable locations for the cooker were not suitable for digging, but less conspicuous areas provided plentifully. I used one wheelbarrow full.
ROCKS - cheap or free. DANGER! USE CAUTION HERE!!! Some stones, especially those collected from a body of water could explode when heated. This might be bad for your health and livelihood. Fair Warning OK? Choose rocks sized between softball and cantaloupe. You want a couple dozen rocks.
PIECE(S) OF PLYWOOD - to cover the cooker during slow cooking. Serves to keep the heat in and keep out potential weather and varmints.
CLOTH - helps hold in the heat for slow cooking; I used an old bed sheet.
To operate the cooker you need:
FIREWOOD - You will burn wood to grill with but the most important thing is to thoroughly heat the rocks for slow cooking. It will take 3-4 hours for the stones to get hot enough.
GREEN LEAFY BRANCHES, PLANT STALKS OR SOAKED WOOD - You need enough to create a moist buffer layer between the hot stones and the pork. The authentic material is freshly cut banana tree stumps. It's wet and fibrous and doesn't burn up, so it creates tasty, smoky steam to cook the pork. In the Mid-Atlantic U.S. I had to use something more local and went with maple and hickory branches with the leaves still on. You could try some other materials too; any type wood that is used for cooking/smoking should work well here. I want to try corn stalks next.
BANANA LEAVES - This is to wrap and flavor the pork. I can get frozen banana leaves at the Latino market near my house for $1 a package. If you can't get banana leaves, you could use foil, but then it won't be Kalua Pig.
CHICKEN WIRE - optional - this helps to cradle and maneuver the pork but you could do without it...
THE MEAT THE MEAT THE MEAT - For day one, pick your favorite grilling foods; steaks, burgers, sausages, chickens, pork chops, lamb, bacon, offal and vegetables too!
For day two it's slow cooking and pork is king. Get a great big pork shoulder, with the skin on. I use the whole shoulder; it should weigh close to 20 pounds. You could do it with less, but it would seem like a lot of work for a little product. This oven is probably capable of cooking two or three whole shoulders if you wanted to. I haven't tried yet.
Step 1: Build the Cooker
First, find a suitable safe place to build your cooker. There is going to be a big hot fire in it, so take proper precautions. Do I need to be more specific? Don't burn anything down or cause property/bodily damage! Ask someone who knows you well if you have any common sense before attempting this step alone. I built my oven on the concrete walkway in my backyard so not to kill a spot on the lawn, but it could be done on bare ground, provided that it is very level.
Stack the blocks on the ground in three layers of eight blocks, as pictured, to produce an open cube shape. The blocks should be straight and level, without big gaps. Be sure that the blocks are stable and will not be knocked over later when you fill them with heavy stones and fire and pork! Now is a good time to check that your grilling grate fits across the top of the cooker.
Next, fill it in with a few inches of dirt, I used a half wheelbarrow full to give about 4 inches of coverage across the bottom of the cooker.
Last step is to cover the dirt with the rocks that you collected.