Preheat oven to 300 degrees. Line two baking sheets with parchment paper
Cream butter, sugar and brown sugar on medium speed for 2 minutes
Add the eggs, vanilla and lemon juice and mix on low speed for 30 seconds, then on medium for 2 minutes
In a smaller bowl whisk together the flour, oats, baking soda, salt and cinnamon
Add the dry flour mixture to the wet ingredients and mix on low speed for 45 seconds or so. (Don't overmix.)
Stir in the chopped walnuts and the chocolate chips
Use a large (3 Tbsp) cookie scoop to portion out the dough, placing cookies about 2 inches apart
Bake at 300 for 20-23 minutes until the edges are brown but the center is still soft
Allow to cool on the baking sheet for one hour before serving