In a medium bowl or 4-cup liquid measuring cup, whisk together the water, evaporated milk, sugar, yeast, salt, egg, and 1 cup of the flour. Add the melted butter and mix until a smooth batter forms. Set aside.
In a large bowl, add the remaining 4 cups flour. Using the large holes of a box grater, grate the 1/2 cup chilled butter into the flour. Toss the flour and butter together until evenly combined. Alternately, you can cut the butter into cubes and cut it into the flour using a pastry blender or two butter knives (or forks) until the butter is in pea-sized pieces.
Pour the yeast mixture over the flour/butter and use a fork or spatula to mix until the dough starts to come together. Mix just until the dough forms a rough, lumpy ball and the flour is evenly moistened (see tutorial above).
Cover the bowl and refrigerate the dough for at least 4 hours and up to 3-4 days.
When ready to make rolls, divide the chilled dough into 4 equal pieces. Roll each piece (or one at a time, depending on how many rolls you want to make - the remaining dough can go back in the fridge) into an 11- or 12-inch circle about 1/4-inch thick or slightly less than. It should be fairly thin. Brush the dough circle with a tablespoon or two of melted butter.
Cut the circle into 8 equal pieces. Roll each wedge into a crescent shape starting at the wide end. Place the rolls on a parchment-lined baking sheet a few inches apart. Cover lightly with a towel or greased plastic wrap and let rise until doubled in size, about 2 hours.
Preheat the oven to 350 degrees F. Bake the rolls for 12-15 minutes until golden and baked through. Out of the oven, brush the tops with melted butter, if desired.
Notes
Make-Ahead: to get even more of a head start, make the dough several days in advance. After rolling and placing the shaped rolls on the baking sheet, cover the tray with greased plastic wrap and place in the refrigerator for up to 18 hours. Take the rolls out several hours before you want to bake them so they can come to room temperature and rise. Bake per the recipe.