Brioche Dough

1. In the bowl of stand mixer, add the warmed milk and 1/2 tablespoon of sugar. Whisk to combine.
2. Next, whisk in the yeast and cover the bowl with a large plate or clean kitchen towel.
3. Allow yeast mixture to sit untouch for 8-10 minutes or until mixture takes on a foamy, bubbly appearance with a fermented aroma.
4. In a medium mixing bowl, add all of the bread flour, 1 cup all-purpose flour, remaining sugar and salt. Whisk ingredients together to combine.
5. In a separate small dish/bowl, add and whisk the egg.
6. With the dough hook attached, add whisked egg into the bowl with the activated yeast mixture and mix at medium speed (4 on stand mixer), about 30-60 seconds.
7. Reduce mixer speed to low (2 on stand mixer) and add all of the dry ingredients into liquid mixture. Continue to mix on low until dough starts to come together and form into a ball, about 1 minute.
8. At this point, start to add and mix the softened butter 1 tablespoon at a time into the dough allowing the previous piece of butter to be fully incorporated before mixing in the next piece of butter.
9. Increase mixer speed to medium (4 on stand mixer) and knead dough for 6 minutes. Dough will be quite soft and tacky to touch.
10. If brioche dough is too soft and difficult to handle, add the remaining 1/4 cup of all-purpose flour 1 tablespoon at a time. May not need to use all of the additional flour, just use enough to prevent dough from being too sticky and more manageable to work with. (Keep in mind that brioche doughs tends to be more soft due to the amount of butter mixed into dough and adding too much flour will result in less fluffy doughnuts. Dough is alot easier to work with after overnight refrigeration.)
11. Transfer dough to a lightly floured surface and shape into a ball. 
12. Grease a large mixing bowl with 1/2 teaspoon of oil. Place shaped dough in greased bowl.
13. Use hand to turn and flip brioche dough in greased bowl. You want all sides of the dough to be coated in oil.
14. Cover bowl with plastic wrap and place in a warm part of the kitchen to rest and rise until it has doubled in size. This can take up to 1 hour or more depending on the warmth of your kitchen.
15. Gently deflate dough with a fisted hand, place a dampen sheet of paper towel over the bowl and cover with plastic wrap. Refrigerate dough overnight. (Do not skip this step, brioche doughs require overnight refrigeration.)
16. The next day, cut a large sheet of parchment paper into 8 (for larger doughnuts) or 10 (for smaller doughnuts) squares, about 3 x 3 inches. It does not need to be precise.
17. Retrieve brioche dough from the refrigerator and transfer to a generously floured surface. Lightly flour the top of the dough.
18. Use a bench scraper or sharp knife to cut dough into 8 equal pieces. For smaller doughnuts, cut dough into 10 equal pieces.
19. Shape each piece of dough into a ball by rolling dough against a clean surface under a cupped hand.
20. Place each ball of brioche dough onto pre-cut squares of parchment paper and evenly arrange on a large baking sheet. Loosely cover the baking sheet with plastic wrap.
21. Place the baking sheet in a warm part of the kitchen and allow balls of brioche dough to rest until doubled in size, about 60-90 minutes.
22. As the shaped dough rest and rise, make cinnamon sugar coating by adding the sugar and ground cinnamon into a shallow dish. Use a fork to mix sugar and cinnamon together to combine.
23. Line a cooling rack with two layers of paper towels. Place the cooling rack near the side of the stove where doughnuts will be fried.
24. Attach a candy/fry thermometer to a deep bottom medium sized pot. Fill the pot with 6-8 cups of oil and heat oil under medium heat to 325-350F (163-177C). Carefully monitor oil. You do not want the temperature to go above 350F(177C).
25. In batches of one to two, carefully place risen balls of brioche dough top side down into oil. Use kitchen tongs to peel parchment square off the back of dough. Fry brioche dough 1 1/2 – 2 minutes per side. Doughnuts will appear puffed with a rich golden-brown color when ready.
26. Using a slotted/spider spoon, transfer fried brioche doughnuts to prepared cooling rack and continue this process until all the doughnuts are fried.
27. Coat all sides of warm brioche doughnuts in cinnamon sugar. Place coated doughnuts on a large serving plate/cooling rack until ready to fill with dulce de leche cream filling. 

Dulce de Leche Cream Filling 

1. In a large chilled bowl, add the cold heavy cream. Using a hand-held electric mixer/whisk, whip the heavy cream to stiff peaks.
2. With a rubber spatula, fold all of the dulce de leche into the whipped heavy cream just until fully incorporated.
3. Cover the top of dulce de leche cream with plastic wrap and refrigerate until ready to use. 

Assembly

1. Transfer dulce de leche cream into a large pastry bag and cut off 1/2 inch from the tip of the pastry bag. May use a small pastry bag and pipe filling into doughnuts in batches.
2. Using a small paring knife, make a slit into the top of each of the doughnuts pushing the knife about 2/3 the way down into doughnuts. Take care to not have the knife go through the opposite end of doughnuts.
3. Fill each of the doughnuts with the dulce de leche cream just until the filling starts to slightly pop out of the slit opening. Doughnuts will start to feel slightly heavier once it is properly filled.
4. Pipe a dollop of remaining dulce de leche cream over the opening of each doughnut.
5. Dust each dollop of dulce de leche cream with ground cinnamon before topping with chocolate curls or mini chocolate chips.