In a measuring cup add warm water and yeast together. Stir together to combine, then allow to sit until it becomes foamy, about 10 minutes. Meanwhile, in a separate bowl, whisk together the flour and the salt, and set aside.

Add buttermilk, beaten egg, butter, and sugar to the stand mixer and whisk together to combine. Add bloomed yeast-milk to stand mixer and whisk to combine. Add the flour/salt to the stand mixer, and mix with a wooden spoon.

Next, attach the dough hook onto the stand mixer, and place on medium-low speed. and mix for around 5-10 minutes for the dough to form. When ready it should be smooth, elastic, and a little bit tacky to the touch.

Transfer dough to a greased large bowl, cover with plastic wrap, then place in a warm area to rise for about two hours, or until the dough is doubled in size.

Turn the proofed dough out onto a lightly floured work surface and roll out to be about ½” thick. Using cookie cutters (I use a 3” cookie cutter), cut out your donuts, then transfer them onto a parchment lined baking sheet. Ensure there is enough space between each donut to allow for rising room (I typically use 2 baking sheets for this).

Meanwhile, add oil to a large wide pot, such as a Dutch oven, filling it about halfway. Heat the oil over medium-high heat until it reaches between 350°F or 375°F. When ready, carefully (don't be too aggressive or the donuts will deflate) pick up the donuts and place them into hot oil, and fry for about 1 ½ minutes per side, or until golden brown. Then place onto paper towel-lined baking sheet to cool off.

Add whipping cream, confectioners sugar, and vanilla, to a large bowl, beat with an electric mixer until stiff peaks have formed. Add mascarpone and kahlua, then continue to beat, just until smooth. Be careful not to overbeat. Keep cold until ready to fill.

When the donuts are cooled to room temperature, add the mascarpone whipped cream filling into a piping bag fitted with a medium-sized round tip. Insert a bamboo skewer about halfway into each donut, then wiggle it around to create a pocket for the filling. Insert the piping bag tip, and squeeze the filling into each donut until each donut is filled with it.

Add chopped chocolate to a microwave proof bowl and place in microwave for 1 minute, or until melted (check at 1 minute, stir, and return to microwave if needed in 20 second intervals until melted).

Once the chocolate has completely melted, add the butter, corn syrup, and espresso powder, then stir together until the butter has melted and everything is well combined.

Transfer glaze to a wide-mouthed bowl, then glaze each donut top with the chocolate glaze and allow the glaze to set for 10-15 minutes before eating.