Best Stuffed Shells

Ingredients (14)

• 1 pound (16 ounces) fresh baby spinach or baby kale, or frozen spinach or kale, or 1 ½ pounds Tuscan kale or spinach bunches, washed and stems removed
• 1 tablespoon extra virgin olive oil
• 12 ounces jumbo shells
• 4 cloves garlic, peeled and cut into several segments 
• 15 ounces (or 1 pound) ricotta cheese or cottage cheese
• 8 ounces (2 cups) grated part-skim mozzarella, divided
• ½ cup (2 ounces) grated Parmesan, plus extra for garnish 
• ¼ cup (⅔-ounce) chives or green onions (mostly green parts), cut into ¼-long pieces 
• Freshly ground pepper, to taste
• ½ teaspoon red pepper flakes, to taste (omit if sensitive to spice)
• ¾ teaspoon fine sea salt, to taste
• 1 large egg, lightly beaten with a fork
• 3 cups (24 ounces) marinara sauce, homemade* or store-bought (I used Rao’s)
• Fresh basil for garnish, optional