Start by making the dough. In a large bowl, combine all the dry ingredients. Then, add the olive oil and gradually incorporate the cold water until it comes together. I often add a few ice cubes in the water to make sure it remains cold (but be careful that they do not fall into the bowl).
Knead on a floured counter until it becomes smooth and only slightly sticky. Cover with a wet towel and let it rest for 30 minutes.
In the meanwhile, start preparing the filling. In a large pan, heat up some oil and cook the onions, the mushrooms and the garlic for about 5 minutes or until the onions become translucent. Add the hard vegetables and finish with the Swiss chard or the spinach. Mix in the lemon juice and the spices and let it cool down a bit.
Preheat the oven at 400°F.
Coming back to the dough, form small balls using about 1/3 cup of dough as you go on. Don’t make them all at the beginning or they will probably dry out by the time you are done. On a floured counter, roll the small ball into a circle, transfer on a baking tray, and add 2-3 tbsp of filling near one edge. You can also add some cubes of mozzarella at this point. Fold over the other half of the dough to cover it. Crimp the edges using your fingers or a fork. Repeat with the rest of the dough.
Brush each empanada with olive oil and bake for 25-30 minutes. For the last 1-2 minutes switch the oven to broil at 450°F for a little more browning and crispiness. Be careful not to burn them!
Serve them with some salsa or guacamole. If you are looking for a guacamole recipe, I have an excellent one here!