Heat on the stove, just until hot enough to dissolve the sugar and salt.
Add the salt, sugar, Creole mustard, lemon juice and lemons, crushed garlic coves, Cajun seasoning and bay leaves. Stir until the salt and sugar has dissolved.
Add the remaining gallon of water, cold would be better as it will cool the brine quicker.
Once the brine has come down to room temperature place the whole pot into the refrigerator, for 2 hours.
Once the brine has become cold slowly drop your turkey into the stock pot and cover.
Allow to sit in the refrigerator for a minimum of 24 hours and up to 2 days.
Remove from the brine and allow the turkey to sit at room temperature for an hour or two before cooking.
Notes
To cool your brine even faster, add ice in the remaining gallon of water.