Grease a medium bowl with olive or coconut oil and set aside.

In a large bowl, combine the dairy-free milk, 1/4 cup (50 g) granulated sugar, and activated yeast. Stir gently with a wooden spoon, then cover the bowl and place it in a warm area for about 10 minutes. The yeast should begin to foam and develop a yeast-like aroma, similar to beer.

Once the yeast is activated, prepare the dough. In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, combine the bread flour and the remaining sugar. Mix briefly to distribute the sugar evenly. Add the dairy-free yogurt, vanilla extract, and the bloomed yeast mixture to the bowl. Mix on medium speed until a shaggy dough forms, approximately 3–4 minutes. Gradually add the vegan butter, one tablespoon at a time, and continue mixing. Pause occasionally to ensure the butter is fully incorporated. Once all the butter is mixed in, increase the mixer speed to high and knead the dough for 10–15 minutes, or until it becomes soft and pliable. The dough may feel slightly tacky but should not stick excessively or leave clumps on your fingers. Test the dough’s readiness by performing the windowpane test.

Place the dough ball into the greased bowl, cover it with a clean dish towel, and let it rest in a warm area (ideally above 80°F) for 60–120 minutes, or until it doubles in size.

Prepare the Filling and Parchment Squares:

While the dough is proofing, prepare the custard filling and lemon curd (if using) according to their respective recipes. Chill the custard in the refrigerator until ready to use. Meanwhile, cut out 8 parchment paper squares (or more if dividing the dough into smaller portions) and arrange them on a baking sheet.

Once the dough has doubled in size, lightly flour a clean surface and place the dough onto it. Divide the dough into 8 equal portions (or more for smaller donuts). For each portion, pinch the corners together to form a ball, then gently roll it between your palms or on the floured surface to smooth out the seams. Place each dough ball onto a parchment square. Repeat with the remaining dough portions.

Cover the baking sheet with the shaped dough balls and let them rest in a warm area for 30–45 minutes, or until they are nearly doubled in size.

With 10–15 minutes remaining in the resting period, pour the sunflower oil into a large saucepan or pot with high walls. Heat the oil to 350–365°F, maintaining a steady temperature. Use a candy thermometer to monitor the heat. Line a cooling rack with paper towels to absorb excess oil after frying.

When the doughnuts are ready, carefully transfer one to a slotted spoon using its parchment square. Remove the parchment and gently lower the doughnut into the hot oil. Fry each side for about 2 minutes, or until golden brown on the bottom, then flip and fry the other side for 1.5 minutes. Depending on the size of your pan, you can fry multiple donuts simultaneously, ensuring the oil temperature stays between 350–365°F. Use the slotted spoon to remove cooked donuts and place them on the prepared cooling rack.

Allow the donuts to cool for about 10 minutes. In a large bowl, add granulated sugar. Dip each doughnut into the sugar, flipping to coat evenly. Repeat for all donuts.

Using a knife or skewer, poke a small hole into the side seam of each donut. Gently move the skewer inside to create a pocket in the center. Fill a pastry bag with the vegan custard (and another with lemon curd if using). Insert the nozzle into the hole and pipe the filling into the donut until it feels full.

Serve the donuts fresh, or store them in an airtight container in the refrigerator for up to 3 days. Enjoy!