Preheat oven to 300F. Line a baking sheet with parchment paper or a silicone baking mat.
Cream butter and sugars in the bowl of a stand mixer on medium speed for about 2 minutes.
Add eggs, vanilla, and lemon juice.
Mix on low for 30 second.
Increase speed to medium, and continue mixing for 2 minutes, scraping down the bowl as necessary.
Add flour, oats, baking soda, salt and cinnamon.
Stir in just until combined. Don’t overmix.
Stir in chocolate chips and walnuts.
Portion dough with a scoop (about 3 tablespoons) onto a baking sheet lined with parchment paper about 2 inches apart.
Bake for 18-23 minutes, or until edges are golden brown and center is still soft.
Remove from oven and cool on baking sheet for about 1 hour.
Notes
Butter: I use salted butter in this recipe. If you use unsalted butter, increase the salt to 1 teaspoon total.
Brown sugar: I use light brown sugar in these cookies.
Flour: To properly measure the flour, either weigh the flour or sift/stir to break it up. Lightly spoon into the measuring cup and level.
Oats: I've only used old-fashioned rolled oats in this recipe.
Chocolate chips: You can use milk or dark chocolate chips if you prefer. If you like more chocolate chips in your cookies, you can increase the chocolate chips to 2-1/2 cups.