In a medium bowl, mix together the milk, hot water, and sugar. The temperature of the mixture should be warm to the touch, but not too hot. Whisk in the yeast. Leave the mixture to sit for about 10 minutes, until the top is covered in a layer of foam.
In the bowl of a stand mixer, mix together the flour, baking soda, and salt. Pour in the yeast mixture and add in the yogurt. Mix together on low speed using the dough hook, until the dry ingredients are moistened, 3-4 minutes. You may need to stop the mixer and use a spatula to scrap down the sides of the bowl as necessary.
Increase the mixer speed to medium, and continue mixing until the dough starts to stick together into a very loose ball, 2-3 minutes. You may need to stop the mixer and scrape the sides of the bowl down as necessary.
Cover the bowl with a kitchen towel, and let it rest for 1 hour.
When the dough is almost ready to be rolled out, heat up the oil in a deep fryer to 375°F / 190°C. Line two large plates with paper towels and set aside.
Flour your work surface and transfer the dough onto the work surface, forming it into a ball. Dust the top of the dough with some flour, and let it rest for 1 minute.
Gently roll out the dough until it is about ½ inch (1-¼ cm) thick. You will feel the bubbles inside the dough stretching.
Using a sharp knife or a pizza cutter, cut the dough into 1-½ inch (4 cm) squares.
Gently drop the beignets one at a time into the oil, being careful not to overcrowd them. I was able to make 4 beignets at a time. Fry each beignet for about 2-3 minutes, turning them frequently with a tong or slotted spoon. Transfer the fried beignets to the prepared plates. Continue to fry the remaining beignets.
Dust each beignet with plenty of powdered sugar, and serve while still warm.