Combine warm milk, sugar, and yeast in a large bowl. Stir and leave 5–10 minutes until foamy. If no foam forms, start over with fresh yeast.
Add salt and flour to the yeast mixture. Stir until a rough dough forms, then knead by hand on a lightly floured surface for 5–6 minutes until smooth and elastic. The dough should be slightly tacky — do not add too much extra flour. Place in an oiled bowl, cover, and rise in a warm spot for 1 hour until doubled.
Punch dough down and divide into 6 equal portions. Stretch or roll each into an oval or round about 6–7 inches wide and 1/4 inch thick. Place on a floured tray, cover, and rest 15 minutes.
Heat vegetable oil in a large deep pot to 350–360°F. Lower one piece of dough carefully into the oil. Fry 2–3 minutes until deep golden, flip, and fry 1–2 minutes more on the second side. Drain on a wire rack or paper towels. Return oil to temperature before each new langos.
Mix grated garlic with olive oil. While langos is still hot, rub garlic oil over the surface. Spread sour cream generously on top. Scatter shredded cheese over the sour cream. Add flaky salt. Serve and eat immediately.
