In a stainless steel pot, combine the water, brown sugar, salt, garlic cloves, peppercorns, bay leaf and rosemary sprigs and bring to a boil. Remove the pot from the heat and stir the liquid to dissolve the salt.
Stir in 3 cups of ice and allow the brine to cool completely.
Next, in a baking dish or food-safe plastic container, cover the pork chops completely in the brine.
Cover tightly with plastic wrap or the lid and refrigerate overnight.
Heat a grill or grill pan to high heat. Heat the oven to 350º.
Remove the pork chops from the brine and pat them dry with a paper towel.
Drizzle the pork chops with grapeseed oil and place them on the grill. Cook for 3 minutes and then turn them 45 degrees and cook for another 3 minutes. (This will give you cool, crosshatched grill marks.)
Flip the pork chops over and cook the second side according to step 7.
If using a grill, transfer the pork chops to a baking pan. Top each pork chop with one tablespoon butter and two thyme sprigs.
Bake the pork chops in the oven until the meat is done, about 10 minutes. The temperature should reach a minimum of 135º on an instant-read thermometer.