Fill a large, heavy-bottomed, wide-mouthed pot halfway with corn oil and heat over a medium-high flame until oil reaches a temperature of 360 degrees F.
While the oil is heating, sift together the flour, baking powder and salt. In another large bowl whisk together sugar and eggs. Stir canola oil and milk into sugar-egg mixture. Stir dry ingredients into egg mixture until a biscuit-like dough forms.
Lightly flour a work surface and turn out the dough. Sprinkle dough lightly with flour and, using a rolling pin, gently roll the dough out to a thickness of 1/8-inch. Using a sharp knife or dough scraper, cut into 2-inch squares. You will have scraps leftover but do not try to remix these as that will cause tough dough; just fry as are.
Use the dough scraper to lift dough squares off the work surface. Fry the beignets in small batches about 4 minutes, or until golden, turning several times to color evenly. Using a slotted spoon gently remove the beignets and drain thoroughly on paper towels. Place powdered sugar in a sieve and shake over the beignets to cover with powdered sugar and serve immediately.