Mix all three ingredients for the overnight preferment until a dough forms. Cover and let sit overnight.

In a small pot, combine whole milk, vanilla bean, salt, and half of the granulated sugar. In a separate bowl, whisk cornstarch with the other half of the sugar, then whisk in the second measurement of milk and egg yolks.

Bring the vanilla milk to a boil. Whisk a small portion into the cornstarch mixture and pour it all back into the pot. Cook on medium-high heat, whisking constantly until thickened and boiling. Boil for another 1-2 minutes while whisking.

Remove from heat and whisk in the butter. Pour into a heat-resistant bowl, cover with plastic wrap, and cool in the fridge.

Once cold, whip the heavy cream, vanilla extract, and sugar to stiff peaks. Fold the whipped cream into the cooled pastry cream.

Lightly warm the milk and whisk in the active dry yeast. Make sure the milk is no hotter than 120℉.

Add remaining ingredients (except the second measurement of sugar) to the mixer bowl. Mix on low speed until a dough forms, then switch to a dough hook and mix on medium-low until passing the windowpane test.

Cover the dough and allow to proof until tripled in size.

Roll out the dough to half an inch thick and cut with a 3" ring cutter. Place on a lightly sprayed sheet pan. Knead and reroll scraps as necessary.

Spray the rounds and cover with plastic wrap. Allow to rise for 30-60 minutes. Prepare frying station, ensuring oil reaches 350-375°F.

Carefully fry donuts for 2-3 minutes on each side until golden brown. Check internal temperature to be at least 190℉.

Remove from oil, drain, and place on a cooling rack.

Allow donuts to cool before filling. Poke a hole in each donut and fill with pastry cream using a piping bag.

In a small pan, add sugar and enough water to make wet sand. Cook on medium-high heat until caramelized to a light amber color.

Dip the tops of the donuts in the caramel and allow to drip off before placing back on the cooling rack.

Allow to cool completely and serve within 1-4 hours at room temperature.