1-First Step: Gather your ingredients for the coffee custard and whisk the 5 large egg yolks with 1 1/2 cups whole milk and 1/2 cup strong coffee in a bowl until well combined. This sets the base for a smooth, creamy filling that really shines in these coffee custard filled donut.

2-Second Step: In a saucepan, whisk together 3/4 cup granulated sugar, 1/4 teaspoon salt, and 1/4 cup cornstarch until it’s all smooth and lump-free. Gradually pour in the egg mixture from the first step, whisking constantly to avoid any clumps forming.

3-Third Step: Add 3 tablespoons butter to the saucepan and cook everything over medium heat. Keep whisking until the mixture boils and thickens, which takes about 1 minute. This is key for that perfect custard texture in your filled donut.

4-Fourth Step: Once thickened, strain the custard through a fine mesh strainer into a bowl to remove any bits. Cover it with plastic wrap so the wrap touches the surface directly, then pop it in the fridge to chill. This step takes about 1 hour, giving you time to move on to the donut.

5-Fifth Step: Start the donut by dissolving 1 pkg active dry yeast (that’s 2 1/4 teaspoons) in 1/4 cup lukewarm water at 110°F, and let it sit for 10 minutes until it gets foamy. This activates the yeast and ensures your dough rises nicely.

6-Sixth Step: In another pan, heat 1 cup whole milk, 1/4 cup shortening, 1/4 cup granulated sugar, and 1 teaspoon salt until it’s almost bubbling, then let it cool to lukewarm. Mix this with the foamy yeast, 3/4 cup mashed potatoes, 2 large beaten eggs, and 5 cups all-purpose flour in a bowl.

7-Seventh Step: Knead the dough until it’s smooth and elastic, which might take 5-10 minutes by hand or with a mixer. Lightly coat it with 1 tablespoon canola oil, cover it, and let it rise in a warm spot until it doubles in size about 1.5 hours. For dietary tweaks, use gluten-free flour here if needed.

8-Eighth Step: Roll out the dough to about 1/2-inch thickness and cut it into 3-4 inch rounds. Place them on greased baking sheets, cover, and let them rise again until doubled, around 30 minutes. This second rise makes them extra fluffy.

9-Ninth Step: Heat 3 cups canola oil in a deep pot to 350°F. Fry the donut for 2 minutes per side until they’re golden brown, then drain them on a wire rack. Be careful with the oil temperature to get even browning without sogginess.

10-Final Step: While the donut are still warm, toss them in a mix of 1/2 cup granulated sugar and 2 teaspoons cinnamon for that crispy coating. Once cooled, fill them with the chilled coffee custard using a piping tip until the centers puff slightly. Serve right away for the best taste the total time is about 3 hours, but it’s worth every minute!