In a mixing bowl, combine flour, sugar, and salt. In a separate bowl, dissolve yeast in warm milk and let it sit for 5 minutes. Add the yeast mixture to the flour mixture and mix until a dough forms.

Knead the dough for about 5 minutes until smooth. Wrap in plastic wrap and refrigerate for at least 30 minutes.

On a floured surface, roll out the dough into a rectangle. Place the cold butter in the center and fold the dough over to encase the butter.

Roll out the dough again into a rectangle and fold it into thirds. Repeat this process two more times, chilling the dough between folds.

Roll out the laminated dough to about 1/2 inch thick. Use a doughnut cutter to cut out shapes. Let them rest for 30 minutes.

Heat oil in a deep fryer to 350°F (175°C). Fry the cronuts until golden brown, about 2-3 minutes per side. Remove and drain on paper towels.

Using a piping bag, fill the cronuts with pastry cream through the side.

Mix powdered sugar, milk, and vanilla to create a glaze. Dip the tops of the filled cronuts into the glaze and let set.