Step 1

Preheat the oven to 300 degrees with racks in the upper and lower thirds of the oven. Line two rimmed baking sheets with parchment paper. (Silicone baking mats can cause the cookies to spread too much.)

Step 2

In the bowl of a stand mixer fitted with the paddle attachment, or with a handheld mixer and a large bowl, combine the butter, granulated sugar and brown sugar on medium speed for about 2 minutes until well-combined and starting to look light and fluffy. Scrape down the sides of the bowl. Add the eggs, vanilla and lemon juice, mixing on low speed for 30 seconds, then medium speed for about 2 minutes, or until light and fluffy. Scrape down the bowl again.

Step 3

With the mixer on low speed, add the flour, oats, baking soda, salt and cinnamon, mixing for about 45 seconds. Don’t overmix. Remove the bowl from the mixer and stir in the chocolate chips and walnuts by hand with a wooden spoon or rubber spatula.

Step 4

Using two large dinner spoons or a generously filled No. 30 (2-tablespoon) disher, scoop the dough into 3-tablespoon (60 grams) portions onto the lined baking sheets, spaced about 2 inches apart. Sprinkle with flaky sea salt, if using. Depending on the size of your scoops, spacing and/or sheets, you may need to do a third batch. If you must reuse one of your first two baking sheets, let it cool completely before scooping and baking the remaining dough.

Step 5

Bake for 20 to 23 minutes, or until the edges are golden brown and the center is still soft. Rotate the baking sheets from front to back and top to bottom halfway through. Let the cookies cool on the baking sheets for about 1 hour.