In a large pot, combine 1 gallon of water, kosher salt, and brown sugar. Heat gently, stirring until the salt and sugar are dissolved. Do not boil.
Remove from heat and let the brine cool slightly. Stir in the bay leaves, peppercorns, crushed garlic, and rosemary.
Once the brine has cooled to room temperature, pour it into a large container or brining bag. Submerge your turkey in the brine, ensuring it is completely covered. If necessary, add more water to cover the turkey. Refrigerate for 12-24 hours.
Remove the turkey from the brine and rinse it thoroughly under cold water to remove excess salt. Pat dry completely with paper towels.
Notes
For best results, use a food-grade container that can hold the turkey and brine. Make sure the turkey is fully submerged.