Place 1 1/2 cups plus 3 tablespoons flour in a medium bowl, and sift in 1/2 teaspoon baking soda.
Place 1/2 cup plus 2 tablespoons dark brown sugar and stir in 1 3/4 teaspoons molasses and 1/2 cup plus 1 teaspoon granulated sugar, breaking up any lumps. Don't worry about the mixture — you're only adding a little bit of molasses so it won't be completely smooth.
Place 1 1/2 sticks unsalted butter in the bowl of a stand mixer fitted with a paddle attachment. Turn to medium-low speed and cream the butter until it has the consistency of mayonnaise and holds a peak when the paddle is lifted.
Add the sugar and molasses mixture (from the second step) to the butter mixture (from the third step) and beat for 3 to 4 minutes, until fluffy.
Use a rubber spatula to scrape down the sides of the bowl and add 1 egg, mixing on low speed for 15 to 30 seconds until just combined. Scrape down the sides of the bowl again. The mixture may look broken, but don't worry about it — overwhipping the eggs could cause the cookies to expand too much during the baking process, and then deflate.
Add the dry ingredients (from the first step) in 2 additions, mixing on low speed for 15 to 30 seconds after each, or until just combined.
Add 2/3 cup chocolate chunks and 1/2 cup semi-sweet chocolate chips and pulse on low speed about 10 times to combine the chocolate into the dough.
Refrigerate the dough for 30 minutes.
While the dough is chilling, position the rack in the center of the oven and preheat to 350 (F).
When the dough has chilled, use an ice cream scoop to divide the cookie dough into 12 equal portions (about 75 grams each). Roll each dough portion into a ball between the palms of your hands.
Bake until golden brown, around 16 - 18 minutes. The cookies are large and will spread out during the baking process — be sure to bake only 4 on each pan, leaving enough space between each dough ball to spread at least 4 inches outwards. When the cookies are finished baking, transfer onto a wire rack to cool completely.