In a small bowl, mix together the warm milk, warm water, and yeast. Let it sit for about 5–10 minutes until it looks foamy and bubbly on top.
In a large bowl, whisk together your flour, sugar, salt, and cinnamon.
Add the softened butter, eggs, vanilla, and your foamy yeast mixture to the flour mix. Stir until everything starts to come together into a shaggy dough. (Don’t worry, it won’t look perfect yet.)
On a lightly floured surface, knead for about 8 minutes, or pop it into a stand mixer with a dough hook and let it do the work for 5–6 minutes. The dough should be soft, smooth, and elastic.
Place your dough into a lightly greased bowl, cover it with a clean towel, and let it rise in a warm spot for about 1 to 1 ½ hours, or until it doubles in size.