Whisk the active dry yeast and warm water together in a small bowl and let stand for 5 minutes.
Heat milk in a small saucepan over medium heat, or in the microwave until just warm.
Combine the melted butter, the Redpath® Dark Brown Sugar, and kosher salt in a large bowl. Stir until the sugar and salt dissolve.
Add the warm milk to the sugar mix and whisk to blend.
Whisk in yeast mixture and the egg.
Add the all-purpose flour to the wet ingredients and stir vigorously with a wooden spoon until a rough dough forms.
Knead dough with lightly floured hands on a lightly floured surface until smooth; 4-5 minutes.
Transfer dough to a lightly oiled bowl, turn to coat and cover loosely with plastic wrap. Let stand at room temperature until doubled; about 1½ hours.
Melt butter in a small saucepan.
Punch down the dough and roll out into one large sheet, approximately ¾ inch (2 cm) thick.
Using two glasses, one large and one small (3½ inches/9 cm and 1½ inches/ 4 cm), begin cutting large donut circles into the dough using the largest glass. Cut each one as close to the other as possible. Once all of the large circles have been pressed, return with the smaller glass pressing it down in the centre of the larger circles to create the holes.
Transfer the cut donuts to a lined baking sheet, transfer the cut donut holes to another. Gather all of the scraps of dough, combine them and roll them out and repeat the process until all of the dough is used.
Using a pastry brush, lightly brush the tops of each donut and each hole with the melted butter. Loosely cover with plastic and leave the covered dough balls out on the counter to proof for 1 hour.
Preheat oven to 350°F (177°C).
Bake donut holes until golden and puffed; 6 to 8 minutes. Bake donuts until golden and puffed; 10 to 12 minutes.
Remove from the oven and allow them to cool for 2 minutes.
Prepare the cinnamon sugar by stirring Redpath® Granulated Sugar and cinnamon in a medium-sized bowl. Pour into a strainer and sift together over a pie plate for rolling and tossing the doughnuts and holes.
Lightly brush each side of the donuts and donut holes with butter, then toss in a bowl with the cinnamon sugar mixture, rolling them around until they are evenly coated.