Preheat oven to 325°F.
In a large bowl, combine the ground beef, mustard, parsley and thyme. Season with salt and pepper. Form into 6 patties (thinner at the center for even cooking). In a large skillet, heat the olive oil on medium-high. Place the patties into the skillet and cook, turning once, about 10 minutes or until cooked all the way through. During the last few minutes of cooking, add the Cooper cheese and cover to melt.
While the patties are cooking, brush the tops of the rolls with water, then sprinkle with kosher salt. Place rolls on a baking sheet and bake until heated through, about 3 minutes. Remove from the oven and split the rolls.
Assemble your sliders:
Divide the patties among the roll bottoms. Add pickles, lettuce, onion, tomato (seasoned with salt and pepper) and mayonnaise. Complete with the roll tops and serve.