Preheat oven to 350°F (180°C). Line a baking sheet with parchment paper.
In a large bowl, whisk together flour, 1/3 cup sugar, 2 1/2 tbsp cinnamon, baking powder, and salt.
In another bowl, whisk eggs, then stir in milk and melted butter.
Gradually add the dry ingredients to the wet ingredients until a smooth batter forms.
Spoon the batter into a piping bag fitted with a small round tip.
Pipe small mounds (6-8 per sheet) onto the baking sheet, spacing 2 inches apart.
Bake 10-12 minutes, until golden on edges.
While donut bites are warm, brush each with 1/2 cup melted (cool to 90°F but still fluid) butter.
Sprinkle with 1/2 cup sugar mixed with 1 tbsp cinnamon, pressing gently.
Let rest 5 minutes for coating to harden.
For ganache: Warm 1/2 cup heavy cream, pour over chopped chocolate in a heatproof bowl. Let sit 2 minutes, then stir until smooth. Drizzle over cooled donut bites.