In a medium mixing bowl, whisk together the warm milk, egg yolks, melted and cooled butter, honey, and vanilla until well combined.
Add the flour, instant yeast, cinnamon, and kosher salt. Stir vigorously for approximately 1–2 minutes, until a thick, sticky, smooth dough forms. The dough should hold some shape when scooped but remain too sticky to roll by hand.
Cover the bowl with plastic wrap, or a clean kitchen towel, and let the dough rise in a warm, draft-free place for approximately 45–60 minutes, or until visibly puffy and aerated.
Pour approximately 3-4 inches of neutral oil into a heavy-bottomed pot, or Dutch oven. Heat to 350°F, using a thermometer to monitor the temperature.
Using a lightly oiled 1-tablespoon cookie scoop or two spoons, gently drop small portions of the risen dough into the hot oil. Avoid stirring or deflating the dough before scooping.
Fry in small batches for approximately 3–4 minutes, turning occasionally, until deeply golden brown and cooked through. Adjust the heat as needed to maintain the oil temperature.
Carefully transfer the fried donut holes to a wire rack set over a baking sheet or a paper towel-lined plate to drain.
Allow the donut holes to cool slightly, then dust generously with powdered sugar. Serve warm.