In a large mixing bowl, gently warm the milk. It should feel lukewarm, about 110°F. Too hot and it will kill the yeast; too cold and it won’t activate properly.
Add the yeast and a teaspoon of sugar to the warm milk. Give it a gentle stir and let it sit for 5-10 minutes until it gets foamy. This is how you know your yeast is alive and ready to work its magic!
Once the yeast is foamy, add the remaining sugar, salt, vegetable oil, and egg to the bowl. Whisk everything together until well combined.
Gradually add the flour, one cup at a time, mixing after each addition. Start with a whisk or spatula, and as the dough thickens, switch to kneading with your hands or dough hooks if using a mixer.
Turn the dough out onto a lightly floured surface. Knead for 5-7 minutes until the dough is smooth and elastic. It should be slightly tacky but not sticky. If it's too sticky, add a tablespoon of flour at a time.
Place the dough in a lightly oiled bowl, turning to coat all sides. Cover the bowl with a clean kitchen towel and let it rise in a warm place for 1 to 1.5 hours, or until doubled in size. This is crucial for that light and airy texture!
While the dough is rising, melt the butter for the filling. In a separate bowl, combine the sugar and cinnamon.
Once the dough has doubled, gently punch it down to release the air. Turn it out onto a lightly floured surface and roll it into a large rectangle, about 12x18 inches.
Brush the melted butter evenly over the dough rectangle, leaving a small border on one long side. Sprinkle the cinnamon-sugar mixture evenly over the buttered dough.
Starting from the long side opposite the border, tightly roll up the dough jelly-roll style. Pinch the seam to seal. Using a sharp knife or bench scraper, cut the roll into 12 even slices.
Arrange the cinnamon rolls cut-side down in a greased 9x13 inch baking pan. Cover loosely with a kitchen towel and let them rise again for 30 minutes in a warm place.
Preheat oven to 350°F (175°C). Bake for 25-30 minutes, or until golden brown and cooked through. Keep an eye on them – ovens vary!
While the bread is baking (or cooling slightly), whisk together powdered sugar, milk, and vanilla extract until smooth. Add more milk, a teaspoon at a time, to reach desired consistency.
Once the bread is slightly cooled (or still warm, if you prefer a meltier glaze), drizzle the glaze over the top. Let it set for a few minutes, then slice, serve, and enjoy every delicious bite!