Preheat the oven to 325°F and line 2 half baking sheets with parchment paper or silicone baking mats.

In a large bowl or stand mixer, beat 3/4 cup butter until creamy (about 1 minute). Scrape the sides and bottom of the bowl.

Add 1 and 1/2 cups packed brown sugar and beat into the butter. Keep scraping and beating for another 2-3 minutes until fluffy.

Add 1 egg, 1 egg yolk, and 2 teaspoons vanilla extract. Beat until everything’s incorporated.

Add 1 cup all-purpose flour, then top it with 1/2 teaspoon baking soda, 3/4 teaspoon baking powder, and 3/4 teaspoon kosher salt. Stir this into the flour.

Use the beaters to stir the flour into the dough but stop when still streaky white. Scrape down the edges.

Mix in 1 cup of old-fashioned oats.

Blend 1 and 1/4 cups oats in a blender or food processor until they resemble coarse flour (30-60 seconds).

Add the blended oat flour to your dough. Beat just until combined, making sure not to overmix!

Gently stir in 2 and 1/2 cups chocolate chips until just incorporated.

Scoop dough (about 1 and 3/4 tablespoons) onto the baking sheets, spacing them 2 inches apart.

Bake for 9-10 minutes. The edges should be firm, but the center might still look slightly shiny.

After baking, use two spoons to gently reshape the cookies as soon as you take them out of the oven.

Let them sit for another 5-10 minutes to set before moving to a wire rack.