Spray a lidded container with cooking spray. Set aside.
Combine flour and yeast in the bowl of a stand mixer fitted with dough hook.
In a small bowl, combine butter, sugar, salt and boiling water.
Stir until butter melts and sugar and salt dissolve.
Mix in evaporated milk.
Set aside to cool.
When milk mixture is lukewarm (about 105℉), beat in egg.
Add liquid ingredients to flour mixture.
Mix at low speed for 3 minutes.
Increase speed to medium.
Mix until it becomes a smooth dough, about 5-6 minutes.
Place in prepared container, cover, and refrigerate overnight.
When you are ready to cook, add 2-3 inches of fresh oil to a shallow 6-8 quart pot.
Heat oil on medium heat to 375 degrees.
While oil is heating, turn dough out onto on a floured surface.
Roll into ¼ inch thick rectangle.
Cut into 2 inch squares.
When oil is hot, carefully add 4-6 beignets, one at a time.
When the beignets rise to the surface of the oil and puff, cook 1-2 minutes.
Flip when lightly browned on bottom.
Cook for 1-2 more minutes.
Remove from oil immediately using a slotted spoon.
Drain on paper towels.
Dust with powdered sugar.