Make the dough: Preheat oven to 350°.
Add the flour mix and salt in a bowl. Make a well in the center. Stir in the vegetable oil and shortening with some water.
Knead the dough until the it becomes uniform. Add the rest of the water slowly. Sprinkle flour on the work surface. Make 2 balls with the dough and let them rest.
Make the filling: Chop the onion into small square pieces. Heat a tablespoon of olive oil in a skillet. Add the chopped onion.
Reduce the heat to medium and cook until the pieces are tender and translucent. Wash the Swiss chard and pinch off the leaves at the top of the stem. Discard the stems.
Meanwhile bring water to boil and cook the Swiss chard for 2 to 3 minutes. Add in the skillet the cooked Swiss chard, the ricotta, Parmesan, provolone, corn starch, salt, nutmeg, and pepper.
Stir and adjust the seasoning to taste. Place the chard filling in a bowl and add 1 egg. Boil the other egg in a small pan.
Assemble the tart: Roll out each ball of dough to a 1/8-inch thickness. Place 1 round of dough in an 8 inch pie plate. Place the Swiss chard filling and the cooked egg onto the dough.
Moisten the edges of the dough with a little water, and then place the top round over the chard filling. Cut away any excess dough (reserve for decorations), crimp, and seal around the edges with water (use your fingertips or a fork).
Cut out decorations for the top of the Pascualina from the reserved dough scraps, and place on top crust. Brush the top of the Pascualina with egg, and bake until lightly browned.