Heat the water to a boil and add spices. You'll want about 5 gallons of water for each 10 pounds of crawfish.
Add lemons, potatoes, garlic, corn, sausage, mushrooms and butter. You want to carefully watch the potatoes and slightly undercook them. This usually takes 10 to 15 minutes. Remember they'll continue to cook after the crawfish are added.
At this point, add your crawfish. This will make the water temperature drop. Bring the water back up and when the water is just about to boil turn off the heat.
Add ice to the crawfish to stop the cooking process. I usually add as much ice as the pot will hold which is approximately 4 to 5 gallons of ice.
This is an important step. Allow the crawfish to sit in the water bath to soak in the spices. We shoot for 45 minutes. The longer they sit, the more spices they'll absorb and the hotter/spicier they'll be.
Serve! Cover a long table with newspaper. Dump the crawfish out on the table and spread them out so they'll cool. Everyone will stand around the table and eat. Have bowls sitting around to collect the shells. Serve with bowls of melted butter and Crawfish Dipping Sauce if desired. However, they are delicious plain.