Ricotta Pie with Spinach, Kale, and Mustard Greens (Torta Rustica) - SippitySup

Ingredients

• ½ teaspoon sea salt (plus more for salting the water)
• 1 pound fresh spinach (stems included)
• ½ pound lacinato kale (cavola nero in Italian) (any very thick stems slightly trimmed)
• ½ pound mustard greens (any very thick stems slightly trimmed)
• 2 tablespoons extra-virgin olive oil
• 1 yellow onion (cut into ¼‑inch dice)
• ¼ cup chopped flat leaf parsley
• ½ pound whole milk ricotta (drained if necessary)
• 1 cup finely grated Parmigiano-Reggiano
• 4 large eggs (divided)
• freshly cracked black pepper (to taste)
• 1 pound prepared puff pastry dough