Step 1To make the crust, sprinkle the yeast over one-fourth cup of the warm water (100 to 110 degrees) and stir to dissolve. Stir in the sugar and set aside while measuring the remaining ingredients.
Step 2Pour the milk, olive oil, salt and remaining one-half cup water into the bowl of an electric mixer. Add the yeast mixture. Mix in enough of the flour to make a bread-like dough. When the dough is smooth, knead dough with a dough hook until it is elastic, 3 to 4 minutes. Remove the dough from the mixer, form it into a ball and place it in an oiled bowl, turning to coat all sides. Cover and let it rise in a warm place until doubled in size, about 1 to 1 1/2 hours.
Step 3To make the filling, combine the diced hearts of palm, tomato, cilantro, parsley, cheeses, onion, avocado and mix until creamy. Season to taste with salt and pepper.
Step 4To make the empanadas, punch down the risen dough and break it into 16 equal pieces. Roll out each piece of dough on a lightly floured surface to a 5-inch diameter about one-eighth inch thick. Place about 1 1/2 tablespoons filling in the center. Brush the edges with egg yolk and fold over to make a half moon. Press down the edges with a fork to seal.
Step 5Deep fry the empanadas in canola oil heated to 350 degrees until golden brown on both sides, about 3 minutes. Serve warm.