In a stand mixer bowl with a dough hook or a large mixing bowl, mix the lukewarm water, granulated sugar, softened butter, egg yolks, yeast, salt, and vanilla extract until combined.

In a separate bowl, whisk together the bread flour and baking powder. Gradually add this to the yeast mixture, mixing until the dough is soft and sticky but pulling away from the sides of the bowl. If the dough is too sticky, feel free to add a little more flour as needed.

Knead the dough for about 10 minutes, either by hand or using your mixer until it’s smooth. Once kneaded, transfer the dough to an oiled bowl, cover it with plastic wrap, and let it rise in a warm place for about 1 hour, or until it has doubled in size.

After the dough has risen, roll it out on a floured surface to a rectangle measuring 10x12 inches. Cut the dough into 12 bars and place them on floured, parchment-lined baking sheets. Let them rise for another hour so they can puff up nicely.

Heat the oil in a saucepan to 350°F (180°C). Fry the doughnuts one at a time for about 1 minute on each side until golden brown. Remember to drain them on a wire rack to cool after frying.

For the glaze, whisk together the powdered sugar, maple syrup, melted butter, and maple extract until smooth. Dip the top half of each doughnut into the glaze and let any excess drip off before placing them back on the wire rack to set.

Serve the doughnuts once the glaze has set. If you have any leftovers, store them in an airtight container at room temperature for up to 1 day.