Butter, for greasing the baking dish
6 large Swiss chard leaves (about 1 1/4 pounds)
Salt
Filling:
2 cups cooked short grain brown rice
1 packed cup baby arugula leaves, chopped
1 cup goat cheese, at room temperature (8 ounces)
1 cup cooked green lentils
1/2 cup chopped fresh mint leaves
1/4 cup extra-virgin olive oil
1 teaspoon kosher salt, plus extra for seasoning
1/2 teaspoon freshly ground black pepper, plus extra for seasoning
2 cloves garlic, minced
One 26-ounce jar marinara or tomato-basil sauce
1/2 cup grated Parmesan (2 ounces)
2 tablespoons olive oil, or unsalted butter diced into 1/4-inch pieces