Position a rack in the center of the oven and heat the oven to 400°F. Let the dough sit at room temperature until pliable, 10 to 15 minutes.
Meanwhile, heat the oil in a 12-inch skillet over medium heat. Add the onion and cook, stirring, until softened, about 3 minutes. Add the chard and cook until tender, 3 to 4 minutes.Remove the skillet from the heat, and stir in the corn, garlic, chile, 1/2 tsp. kosher salt, and a pinch pepper. Transfer to a large plate or rimmed baking sheet to cool, then toss with 1 Tbs. of the mint.
In a small bowl, whisk the whole egg and cream. In a large bowl, combine the ricotta, Parmigiano, the remaining 1 Tbs. mint, the egg yolk, 1/2 tsp. kosher salt, and a pinch pepper. Reserve 1/4 cup of the cheese mixture. Gently mix the remaining cheese mixture with the Swiss chard mixture.
Roll the dough between 2 sheets of lightly floured parchment paper into a 14-inch round, loosening the parchment from the dough occasionally and adding a bit more flour if it sticks. Transfer on the parchment to a baking sheet; remove and discard the top sheet of parchment.
Leaving a 2-inch border, spread the chard mixture over the dough, then dollop with the reserved cheese mixture.
Fold the edge of the dough up and over the filling. If the dough is sticking to the parchment, refrigerate it for 5 to 10 minutes, and then continue folding. Brush the folded dough with the egg wash.
Bake, rotating the baking sheet once halfway through, until the crust is golden brown, 40 to 50 minutes. Transfer to a cooling rack, season generously with flaky sea salt, and let cool for 10 to 15 minutes. Serve warm or at room temperature.
nutrition information (per serving):
510, Fat Calories
32, Saturated Fat
17, Polyunsaturated Fat
2, Monounsaturated Fat
Photo: Scott Phillips