Preheat to 425°F (220°C)
In a large bowl, whisk together flour, baking powder, salt, and sugar (if using).
Add cold butter and shortening. Using a pastry cutter or fingertips, work the fat into the flour until it resembles coarse crumbs with pea-sized bits of butter throughout.
Pour in evaporated milk, stirring gently with a fork until the dough begins to come together. Do not overmix.
Turn the dough out onto a lightly floured surface. Gently pat or roll to about ¾ inch thick. Fold once or twice for extra layers, then cut into rounds or squares.
Place biscuits on the prepared baking sheet, close but not touching for soft sides, or spaced apart for crisp edges.
Bake for 14–16 minutes, or until golden on top and bottom.
Brush the tops with melted butter after baking for a glossy finish.
Best served warm — especially with jam, cheese, or a savory island breakfast.