Sift the flour with the salt into a large bowl. Cut the lard and butter into little pieces and rub into the flour until it resembles coarse crumbs. Make a well in the center of the flour and stir in the egg yolks. Add the cold water a tablespoon at a time until the dough is soft but not sticky. Cover with plastic and refrigerate at least 1 hour.
Mash the sardines with the lime juice and cilantro and set aside. Bring a large pot of salted water to a boil and immerse the Swiss chard in the boiling water for a few seconds. Drain thoroughly and squeeze dry. Chop the chard, both leaves and stems, and set aside.
Heat the butter and olive oil in a large skillet over moderate heat. Add the onion and saute until soft, 3 to 5 minutes. Add the garlic, jalapeno and salt and pepper, and saute another minute to release the aromas. Add the Swiss chard and cook until blended. Remove from the heat, season with salt to taste and set aside.
Roll the dough out on a lightly floured surface to 1/8-inch thickness. Use a round cookie cutter to cut 15-20 circles about 1-inch larger than the circumference of muffin or cupcake tins. (The muffin tins should be about 2 1/2inches in diameter). Use another round cutter to cut the same number of circles the same size as the tins. Press the larger circles into the tins.
Preheat the oven to 350 degrees F. Add enough of the Swiss chard mixture to each tin to come about two thirds of the way up the tin. Divide the sardine filling among the tins. Whisk together the egg and water. Moisten the edges of the pastry with a little of the egg wash. Cover the filling with the smaller circles of pastry and seal the edges, pressing together with your fingers. Brush the tops with more of the egg wash and bake for 30 minutes, or until golden.