Combine yeast and 1 teaspoon of sugar then slowly whisk in milk. Allow mixture to sit for 10-15 minutes. Once it's foamy, stir in egg yolks and vanilla until combined
Add your yeast mixture, flour, butter, salt, and sugar to a large bowl. Knead for 5-10 minutes until the dough becomes soft and elastic.
Move the dough to a lightly greased bowl and cover it with a clean kitchen towel. Leave your dough in a warm, dry place to rise for 1-2 hours or until it doubles in size.
Custard
While your dough is rising, heat the milk and vanilla in a medium saucepan over medium heat. Bring to a simmer.
Whisk together sugar, cornstarch, salt, and egg yolks in a medium bowl until the color becomes lighter.
Very slowly whisk your hot milk into your egg yolk mixture. Do this too fast, and your yolks will turn to scrambled eggs.
Pour this mixture through a sifter back into the saucepan. Continue whisking over medium heat until it begins bubbling and starts to thicken. Remove from heat and whisk in the butter.
Transfer the custard to a bowl and cover it with plastic wrap. To prevent a skin from forming on top, ensure you press the wrap directly against the surface of the custard. Store it in the fridge for 1-2 hours or until the custard has completely cooled.
Donuts
Turn your risen dough onto a lightly floured surface and punch it down. Roll out to about ½ inch thick
Using a 3" round cookie cutter, cut rounds from the dough. Cut as many as you can, roll the remaining dough back into a ball, and repeat these 2 steps until you have used all the dough.
Place each donut round on a lightly greased baking sheet to rise for 20-30 minutes. They will double in size, so leave about 1" of space in between each donut.
Heat oil in a large pot or skillet to 360F. Carefully place donuts in the oil and cook for 1 or 2 minutes on each side or until golden brown. Will will need to be done in batches
Carefully remove the donuts from the oil using a slotted spoon to drain the excess oil. Place donuts on a paper towel-lined plate while you fry the remaining rounds.
Fill
Fill a piping bag with your custard and fit it with a piping tip.
Run a chopstick or skewer through your donut to create a pocket for the custard. Insert the tip of your piping bag into one side of the donut and squeeze to fill it with custard. Repeat with remaining donuts.
Brulee
Heat sugar, lemon juice, and water in a small saucepan over medium-high heat. Bring mixture to a boil, then reduce heat to medium. Give the pan a gentle swirl occasionally. Once the sugar has turned golden brown, remove your pan from the heat and swirl until the brown color deepens.
Carefully dip the top of each donut onto the caramel, and tilt the donut away from you, allowing the excess to drip off before placing it aside to cool.
If the caramel mixture begins to harden, return it to the heat and continue swirling until it warms up and becomes more liquid.
Sprinkle a pinch of powdered sugar and a few strawberry slices on top of each donut once the caramel hardens.
Notes
This creme brulee donut recipe is easy to follow but you have to pay close attention at each stage. Each element is very delicate and can burn very quickly so it's important to keep a close eye on everything as it cooks.
The caramel is going to be incredibly hot so I recommend wearing gloves to protect your hand from getting burned during the dipping process.