First you will need to purge the crawfish. Place them in a tub of clean water for about 15 minutes.
Fill the large pot half full with fresh water, place on outdoor propane cooker, and start the fire. Place the lid on the pot and bring the water to a boil.
Add 1/3 lb of your seafood boil. Let the boiling water mix it well for a minute or so.
Drop in the onions (halved), the potatoes and fresh garlic. Let this cook, keeping an eye on the potatoes. (Check for doneness by stabbing with a sharp knife or fork. If it goes in easy, it is cooked. Hint, Do not over cook potatoes, slightly under cook them because they will continue to steam and cook in the ice chest. You don't want to end up with mashed potatoes.) When the potatoes are almost done, add the corn and mushrooms. After they have cooked, lower the fire on the burner and remove the basket. Place the vegetables in a small clean ice chest - don't close the lid - just place foil on top.
Turn the heat up on the burner. Add more spice to the water. (About 1/2 lb., save the rest of the spice for later). Take the lemons (halved) and squeeze the juice in the water. Then add the lemons to the water. When the water comes to a boil place the crawfish into the basket and put the basket in the pot. (Be careful - it's very hot!) Put the lid on the pot.
When the water comes back to a boil - keep a very close eye on this part - let it boil for 4 minutes and turn off the fire. Let it soak for another 3 minutes and then remove. Kill the boil by adding cold water or ice, not much is needed maybe a gallon or so. Then let the crawfish soak. They will sink to the bottom and fill with spicy water (JUICES).
Get an old table and place old newspapers on top. Dump the basket of crawfish on top of the newspaper and sprinkle with leftover spice.
Dump the onions, potatoes, corn and garlic on top of the crawfish. The vegetables are for those guests who cannot figure out how to peel the crawfish. At least they won't starve.