Cream butter, sugar, and brown sugar in the bowl of a stand mixer on medium speed .
Add eggs, vanilla and lemon juice, blending with mixer on low speed for 30 seconds, then medium speed for about 2 minutes, or until light and fluffy, scraping down bowl.
With mixer on low speed, add flour, oats, baking soda, salt and cinnamon, blending for about 45 seconds. Don’t overmix.
Remove bowl from mixer and 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 6 cookies to a sheet.
Preheat oven to 300°F. Bake for 20 to 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.
Video
Notes
My notes: I made this recipe a few times and found that adding an additional ¼ cup of flour gave me the consistency that I wanted. I'm not saying that you need to do that. Make them as written the first time! Every kitchen is different, depending on the pans you use, your oven, and humidity and altitude levels. This was the only tweak that I made.