Make the filling: Add a tablespoon of water to a large stock pot and add the spinach. Cover and let steam until just wilted, about 3 minutes. Stirring half-way through. Be careful to not overcook the spinach. Drain and let cool completely. Squeeze the spinach to remove all of the excess water and finely chop.
In a large skillet, sauté the oil, garlic, and spinach for 2 minutes. Transfer the mixture to a medium bowl to cool.
Add the egg and Parmigiano-Reggiano cheese to the spinach mixture and mix until well incorporated. Gently fold in the ricotta cheese, leaving small pieces of the ricotta visible in the mixture. Do not overmix.
Make the dough: In a medium bowl, combine the flour, salt, and baking powder. Add the oil and press together with your fingers until the dough is crumbly. Add the water, wine, one whole egg, and one egg white and knead the dough with your hands in the bowl until incorporated and the dough forms a smooth ball. Cover and let the dough rest for 10 minutes.
Lightly dust a 16-inch piece of parchment paper and transfer three quarters of the dough to it. Dust the top of the dough with flour and place another 16-inch piece of parchment paper on top. Roll the dough between the parchment into a 14-inch circle. Remove the top piece of parchment and invert the dough into an ungreased fluted 11-inch tart pan and slowly remove the second piece of parchment. Gently lift the edges of the dough and lightly guide the dough into the side of the pan, letting the excess dough drape over the edge. Pass over the edges of the pan with your rolling pin to cut the fluted edges in the dough. Gather the scraps and add to the reserved dough.
Evenly cover the bottom of the tart with the slices of Mortadella. Add the provolone cheese, overlapping the slices to cover the Mortadella. Spoon the spinach mixture into the tart and smooth with an off-set spatula.
Dust a piece of parchment paper with flour and place the remaining dough on it. Dust the top of the dough with flour and place another piece of parchment on top. Roll the dough between the parchment into an 8 x 12 rectangle. Remove the top piece of parchment and use a pastry wheel to cut ¾-inch wide strips of dough. Arrange the strips across the tart, leaving a ½-inch space between them, then rotate the pan slightly and place more strips on top at a 45-degree angle.
In a small bowl, mix the reserved egg yolk and 1 teaspoon of water and brush the top of the lattice and the fluted edge.
Bake for 45 minutes until the filling is bubbling and the crust is golden. Let cool for 15 minutes, then remove the tart ring.