Next, gradually add your butter; add two pieces of butter at a time, beating after each addition. Then, mix for about 5 to 6 minutes. Or until your butter becomes fully incorporated, and your dough becomes soft.

Then, place your medium-sized saucepan over medium heat. And warm your milk until you observe bubbles forming around the edges. With that, avoid bringing the milk to a boil.

After that, remove your saucepan from the heat. And carefully drizzle the warm milk into your egg mixture while whisking constantly. Then, scrape your egg mixture back into the saucepan. And place the saucepan over medium heat. Be sure to whisk constantly for 3 minutes until your mixture thickens. In addition to that, it comes to a boil.

Next, boil and whisk for about 10 seconds. Then, wait for the cream to become thick and glossy. In addition to that, it no longer has foam on top. When this occurs, ensure to remove the saucepan from the heat as soon as possible.

Then, pour your white cream filling through a sieve that you set over a small bowl. Once you finish sieving your cream, whisk in your vanilla. After that, cover your bowl with plastic cling wrap. And press the plastic wrap against the surface of your pastry cream. Doing this avoids skin from forming.

Lastly, place your white cream into the refrigerator for 4 hours. Or until chilled. Keep in mind that you can refrigerate your cream for up to 3 days.

Then, take your prepared dough from the refrigerator. And ensure to place it on your well-floured work surface. After that, gently roll your dough into a 12-inch square with a 1/2 inch thickness using a rolling pin.

Afterward, cut out your dough using a round cutter. And ensure to cut about nine donuts. Next, transfer your donuts into your prepared baking sheet. And cover it with plastic cling wrap sprayed with a non-stick cooking spray. Then, place your baking sheet into a warm area for about 2 to 3 hours. And wait until your donuts double in height and become puffy.

Next, fill your large pot with about 3 inches of oil. And place it over medium heat. Use a deep-fry thermometer. In addition to that, measure the temperature of your oil. With that, the oil must reach 350 degrees Fahrenheit.

While waiting for your oil to heat, line the baking sheet with two layers of paper towels. You do this to drain the donuts. Pour some sugar into a smaller bowl and set it aside.

Afterward, be sure to place three donuts at a time. With that, carefully place your donuts into your hot oil. And fry your donuts for two to three minutes until they become golden brown on the underside. Also, gently turn your donuts over. And ensure to fry for two to three minutes or until the other side becomes golden brown.

After that, use a slotted spoon. And remove your donuts from the oil into the baking sheet lined with paper towels. Then, repeat the steps until you fried all the donuts.

When your donuts are cool enough to touch, toss them into the sugar one at a time. Doing this, coat your donuts evenly. After that, return your donuts to the baking sheet lined with paper towels. Then, allow your donuts to cool completely for about 30 to 40 minutes.

While waiting for your donuts to cool completely, beat your heavy cream using an electric mixer. Do it at medium-high speed until stiff peak. Afterward, whisk your chilled cream to loosen it up. And gently fold in about one-third of your whipped cream. After that, fold your remaining whipped cream until there are no longer visible white streaks. Next, transfer your white cream into a piping bag.

Lastly, poke a hole in each of your donuts. And fill them with your white cream filling. Once you fill all the donuts, you can serve and enjoy. Always remember, serve your donuts fresh.