In a mixing bowl (or large bowl), whisk together cake flour, bread flour, baking soda, baking powder, sea salt, and espresso powder (if using). Don’t add the finishing salt yet.

Make sure there are no lumps; whisk until uniform.

In a separate mixing bowl (use your stand mixer or hand mixer), cream the softened butter, brown sugar, and granulated sugar together. Use medium speed, about 2 to 3 minutes, until the mixture is light and fluffy (but don’t overdo it).

Scrape down the sides of the bowl with a spatula to make sure everything is incorporated.

Add the egg and egg yolks, one at a time, mixing briefly after each addition.

Add vanilla extract and mix until just combined.

Reduce mixer speed to low. Gradually add the flour mixture into the wet mixture.

Mix only until just combined — it’s okay if a few streaks of flour remain. Do not overmix.

Use a spatula to fold in the mini chocolate chips until evenly distributed.

Divide the dough into four equal parts (you can eyeball it).

Shape each part into a rectangular disk about ½ inch thick.

Wrap each disk in plastic wrap.

Chill in the freezer for about 45 minutes. (You can chill longer — 2 hours or overnight works too.)

My experience tip: I found the cookie texture more reliable when the dough is colder. Once, I skipped chilling and the cookies spread too much and became too flat. Chilling gives you control.

Preheat your oven to 350 °F (175 °C).

Line your baking sheets with parchment paper (or silicone mats).

Take one chilled disk, unwrap it, and lightly roll with a rolling pin (still wrapped) just to even it out.

Unwrap and use a pizza cutter or knife to cut into roughly ½-inch strips, then cross-cut into ~½-inch squares. These are your cookie dough pieces (tiny, like thumbnails).

As you cut, place the pieces on the parchment-lined baking sheet, leaving ~1 inch between them.

Bake for 6 to 8 minutes. Aim to bake until edges are just set but centers still look a tad soft.

The cookies will continue to cook a little after you remove them.

Immediately after removing from oven, sprinkle a light pinch of finishing salt over the cookies.

Let the cookies rest on the baking sheet for ~3–5 minutes (they firm up as they cool).

Then transfer them to a cooling rack.

Continue with the remaining dough, baking in batches until all cookie pieces are done.