Preheat your oven to 180°C (360°F) and line a baking sheet with parchment paper. While the oven heats, measure out all your ingredients: softened butter, brown sugar, sweetened condensed milk, vanilla extract, salt, flour, rolled oats, baking powder, cinnamon, and chocolate chips. Having everything measured and ready before you start mixing ensures a smooth baking process and prevents mistakes.

In a medium bowl, combine the softened butter, brown sugar, and sweetened condensed milk. Beat with a hand mixer or whisk vigorously for about 2-3 minutes until the mixture becomes light and fluffy—this incorporation of air is what gives these cookies their tender texture. Add the vanilla extract and mix until fully combined. I find that creaming this mixture thoroughly makes a real difference in how soft the final cookies turn out.

In a separate small bowl, whisk together the flour, baking powder, salt, cinnamon, and rolled oats. This ensures the leavening agent and spices are evenly distributed throughout the dough. Gently fold the dry mixture from this step into the creamed butter mixture from Step 2 until just combined—don't overmix, as this can make the cookies tough. The batter should come together into a cohesive dough.

Fold the chocolate chips into the dough from Step 3 until evenly distributed. Using a small cookie scoop or spoon, roll the dough into balls about the size of walnuts and place them on the prepared baking sheet, spacing them about 2 inches apart. With the back of a fork, gently press each ball to create a slight thickness and a textured surface—this helps them bake more evenly and gives them that classic cookie appearance. I like to use a fork dipped in water so it doesn't stick to the dough.

Bake in the preheated 180°C (360°F) oven for 15 minutes, or until the edges are lightly golden brown but the centers still look slightly underdone—they'll continue cooking on the hot pan after removal. Remove from the oven and let the cookies cool on the baking sheet for 5 minutes to allow them to set, then transfer to a wire rack to cool completely. This two-stage cooling prevents them from breaking apart while keeping them tender.