Whisk together the flour, baking soda, salt, and cinnamon in a medium bowl. This ensures the leavening agent and spices are evenly distributed throughout the dough, preventing pockets of baking soda that could create off-flavors. Set this mixture aside while you prepare the wet ingredients.

Using an electric mixer, beat the softened butter with the granulated sugar and brown sugar until the mixture is pale, fluffy, and noticeably increased in volume, about 2-3 minutes. This creaming process incorporates air into the dough, which helps create tender, lighter-textured cookies. I find that starting with softened butter (not cold) makes this step much quicker and more effective.

Add the blackstrap molasses and vanilla extract to the creamed mixture and beat for 30 seconds to incorporate. Then add the room-temperature egg and mix for about 1 minute until everything is well combined and the mixture looks smooth and slightly fluffy. Room-temperature eggs incorporate more smoothly and help create a more uniform batter.

Add the dry ingredient mixture from Step 1 to the wet ingredients and mix on low speed just until the flour is incorporated and no dry streaks remain. Overmixing at this stage can develop too much gluten, resulting in tough cookies instead of tender ones. Mix just until everything comes together.

Fold the rolled oats and chocolate chips into the dough using a spatula or sturdy spoon until evenly distributed. The oats add chewiness and nutty flavor, while the chocolate chips provide pockets of sweetness and richness. I like to use a mix of folding motions to keep the dough light and ensure the chips are scattered throughout rather than clumped.

Transfer the dough to a bowl, cover it, and refrigerate for at least 1 hour (or up to 24 hours). While the dough chills, preheat your oven to 375°F about 15 minutes before you plan to bake. Chilling allows the flavors to develop and helps prevent the cookies from spreading too much during baking.

Scoop the chilled dough into 1.5-inch balls and place them 2 inches apart on parchment-lined baking sheets. Bake for 8 to 10 minutes, until the edges are golden brown but the centers still appear slightly underbaked. Let the cookies cool on the baking sheet for 2 minutes to set slightly, then transfer them to a wire cooling rack to cool completely. This resting period on the hot sheet allows them to firm up enough to move without breaking.