Place yeast into the mixing bowl of a large stand mixer. Whisk in warm water and let stand until a creamy foam forms on top, about 5 minutes. Add salt, sugar, milk, 2 tablespoon of melted butter, vanilla extract, egg, and ground cinnamon. Whisk together thoroughly. Pour flour on top of liquid ingredients. Place mixing bowls onto mixer.
Attach dough hook to mixer and knead on low speed until the dough comes together in a ball and becomes soft and sticky, about 3 minutes. Dough will stick to the hook and pull away from the side of the bowl.
Transfer dough to a floured work surface, knead 2 or 3 times, and shape into a ball. Wrap dough in plastic wrapand refridgerate for 20 minutes to let the gluten relax.
Remove dough from the fridge, unwrap, and dust lightly with flour. Roll out into a 9x18 in rectangle about ¼ in thick. Evenly spread 6 tablespoons softened butter onto the middle third of the dough. Fold one unbuttered third over the buttered third and press lightly; spread remaining 6 tablespoons of butter on top of the third. Fold remaining third over the first (buttered) third. Transfer dough onto a sheet pan, cover lightly with plastic wrap and a kitchen towel, and refridgerate 20-30 more minutes for the butter to become firm. Sprinkle dough lightly with flour as you work if it becomes sticky.
Return dough to the floured work surface and pat very gently into a 8x14 rectangle about ½ in thick. Fold outer thirds over center third as before; roll out into an 8x14 in rectangle again. Keep edges of rectangle as straight as possible. Fold in thirds as before. Cover dough lightly with a kitchen towel, and refrigerate for 2 hours.
Roll the dough out to ⅜ in thick. Cut dough in half cross wise. Leave half on a lightly floured surface; refigerate other half of dough until needed.
Using a sharp 3-inch circular cutter to cut 8 circles of dough from piece on the work surface. Use 1-inch size cutter to cut the donut holes out of the dough circles.
Line a baking sheet with waxed paper and sprinkle lightly with flour. Arrnage cronuts and holes onto a prepared baking sheet. Let rise in a draft free, warm place (inside unheated oven) until doubled in size, about 1 hour.