In a mixing bowl, combine milk and yeast. Let stand for 5 minutes or until foamy. Add the eggs, sugar, oil and salt. Stir everything with a wooden spoon. Add 4 cups of flour, one cup at a time while stirring. The mixture will turn into a shaggy dough.
Sprinkle just enough of the remaining 1/2 cup of flour and keep stirring until the dough gathers in the center. Turn the dough over on a floured board and knead it until it is smooth and elastic, about 6-10 minutes. As you knead, dust your hands and your board as needed to help with the stickiness. You may need to use up to 1/8 cup of additional flour.
Shape the dough into a ball and place it a bowl. Cover and let rise for 1 and 1/2 hours, or until the size is doubled. You can make the filling at this point.
Gently punch the dough down and divide it into 18-20 portions. Using a small rolling pin or your hands, flatten each portion into an oval that is about the size of your hands. Spread about a tablespoon of the filling across the surface of the dough and roll it into a log. Repeat with all the other portions. Arrange the rolls in a large baking tray that is greased or lined with parchment paper. Brush evaporated milk on each of the rolls and dip them in breadcrumbs. Cover them loosely with plastic wrap and let them rise for an hour.
Preheat the oven to 350 F. Bake the Spanish bread for 15-20 minutes, or until the rolls are lightly golden.
Heat the butter in a small saucepan until it is bubbly. Add the flour and the breadcrumbs and stir the mixture vigorously with a wire whisk for a few seconds. This is a grainy mixture at this point. Immediately add the milk and keep stirring until the mixture loosens up a bit. Stir for 30 seconds more and turn off heat. Stir in the sugar well until it is incorporated. Set aside to cool. This mixture is a chunky paste.