Add the milk, butter, sugar and salt to a saucepan and heat, stirring until the butter is melted and the sugar is dissolved. Remove from heat and set aside to cool until lukewarm.
Mix the warm water and yeast together in a small bowl and set aside for 5-10 minutes to activate the yeast.
Add 4 cups of the flour to large mixing bowl. Make a well in the center of the flour and add the yeast mixture, warm milk and beaten eggs. Stir with a wooden spoon to mix the ingredients and bring the dough together.
Remove the dough to a floured work surface and knead, adding extra flour as needed until the dough is no longer sticking to your hands and is silky and elastic. Remove the dough to a large, lightly oiled bowl. Cover with a clean towel or plastic wrap and set in a warm corner until doubled in size, about 1 to 1 1/2 hours.
Remove the dough to a lightly floured work surface and punch it down with your fists to deflate it. Cut the dough into 2 equal-sized portions. Roll out one of the portions out to fit the bottom of a greased, 11x17-inch baking pan. Place the dough in the baking pan and trim it to fit, saving the trimmings. Mix together the pineapple preserves and cinnamon and spread over the bottom dough, leaving a 1-inch border around the edges.
6. Cut about 1/4 of the dough off the second doughball and set it aside. Roll the remaining dough out to fit the baking pan as a top for the semita. Lay the second layer over the pineapple filling and trim it to fit the pan. Press down the edges of the semita with a fork to seal. Knead the remaining dough and trimmings into a ball and roll it out to around 1/4-inch thick and about 10 inches long. Cut the dough into long strips about 1/4-inch wide.
Preheat oven to 350°F Beat the remaining egg with the milk or water. Brush the top of the semita with the egg wash. Lay the strips of dough on the semita in a criss-cross pattern, trimming them to fit. Brush the dough strips with egg wash and sprinkle the whole top of the pastry with a liberal amount of sugar. Set the semita aside to rest for about 30 minutes.
Poke the semita all over with a toothpick to prevent the pastry from overpuffing as it bakes. Bake for 30 to 40 minutes, or until the semita is golden brown on top. Remove and cool. Cut into 12 portions and serve with coffee, tea or hot chocolate.