Combine yeast and warm water in a 2-cup liquid measuring cup; let stand 5 minutes.
Combine yeast mixture, evaporated milk, and next 3 ingredients. Gradually stir in enough flour to make a soft dough. Cover and chill 8 hours.
Turn dough out onto a well-floured surface; knead 5 or 6 times. Roll dough into a 15- x 12 1/2-inch rectangle; cut into 2 1/2-inch squares.
Pour oil to depth of 3 to 4 inches into a Dutch oven; heat to 375°. Fry 3 or 4 beignets at a time, 1 minute on each side or until golden. Drain; sprinkle with powdered sugar.