Preheat the oven to 350°F (177°C). Line a baking sheet with parchment paper.
To heat-treat the flour, spread the flour into an even layer on the lined baking sheet and place it into the preheated oven. Bake for 5 to 10 minutes or until the temperature of the flour reaches 160°F (71°C). To evenly heat the flour, rotate pan and stir the flour every 3 minutes or so while also checking the temperature (see Chef’s Tips).
Transfer the treated flour to a large bowl. Sprinkle in the salt and ground cinnamon. Whisk well until no lumps remain. Set aside to cool; 30 minutes.
In the bowl of a stand mixer fitted with the paddle attachment, cream butter until smooth. Add in the Redpath® Dark Brown Sugar and cream until pale in colour; 2 to 3 minutes. Scrape down the sides of the bowl and mix in the vanilla extract until well combined.
Add in the cooled flour mixture. Mix on low speed until just combined. Drizzle in the milk. Mix on medium speed until well incorporated. Stir in the chopped semi-sweet and milk chocolate on low speed or fold in by hand using a large rubber spatula.
Line the second baking sheet with parchment paper.
Using a small-trigger-style ice cream scoop or a tablespoon measuring spoon (these will be slightly smaller), scoop evenly sized balls of dough onto the parchment-lined baking sheet (see Chef’s Tips). Place into the freezer for 10 minutes. Roll dough into balls and place back into the freezer to firm up; 20 minutes.