MELT the butter in a large skillet over medium heat, then cook, swirling the pan frequently, until lightly browned, 2 to 3 minutes. Carefully pour out the butter into a bowl, allowing any burnt solids to stay in the bottom of the skillet. Wipe the skillet clean with a couple of folded paper towels, then return the brown butter to the skillet and heat it again over medium heat. Add 1 piece of sage to test the butter for readiness: It should immediately sizzle. When the butter is hot enough, scatter the remaining sage into it and cook, turning the leaves often with a slotted spoon, until they are crispy, 20 to 40 seconds. Using a slotted spoon, transfer the fried sage to paper towels to drain. Season it lightly with salt.