In a small bowl, mix together yeast, sugar, and lukewarm water. Leave undisturbed for 5 minutes until the mixture gets foamy.
In your mixer bowl, whisk together flours and salt.
Add yeast mixture to flour mixture. Attach dough hook, then mix on the lowest setting for a minute to distribute yeast.
With mixer still on the lowest setting, gradually pour in milk and canola oil. Increase speed to low and knead dough until it’s smooth and soft, 5–8 minutes.
Tip dough out onto a clean work surface and form into a ball. Lightly grease inside of a large bowl with canola oil. Place dough into bowl and roll around to coat all sides with oil. Cover bowl with beeswax wrap or cling film and place in a warm, dry spot and leave undisturbed until dough has doubled in bulk, about 2 hours.
Lightly grease a rimmed 9" x 13" or 9" x 15" metal baking pan with canola oil.
After dough has doubled in size, punch it down to release excess gas build-up. Turn out onto a lightly floured surface and—with a rolling pin—roll dough into roughly the size of your pan. Gently transfer dough to prepared pan.
Cover pan with a clean kitchen towel, then place in a warm, dry spot and leave undisturbed for 20 minutes to rise.
While dough is proofing, heat oven to 375°F.
After the second rise, semi-aggressively poke all over the dough with your fingers. Drizzle chili crisp on top, gently spreading/rearranging crispy bits as necessary. If using, sprinkle kosher salt on top.
Bake for 25–30 minutes until edges are golden brown.
Transfer pan to wire rack and allow to cool a smidge. Then slice and serve warm (with additional chili crisp if want it extra spiiicy!).