Preheat oven to: 350 degrees (F)
In a mixing bowl, combine the dry ingredients (flour, cinnamon, salt, baking powder, and baking soda) and whisk together.
In the Kitchenaid mixer bowl, use the paddle attachment at medium speed to cream together the butter and sugars. Add the eggs one at a time. Add the vanilla.
While the mixer goes, SLOWLY add in the dry ingredient mixture (slowly, or else it flies out everywhere). Then mix in the oats, raisins, and walnuts.
Put the batter in the fridge for 30 minutes or so ... cold batter is easier to work with.
I want large, soft cookies, so divide the resulting dough for exactly 24, or about 54g per cookie. In any case, 55g is an upper limit, for this or the standard toll house cookie recipe ... bigger than this and the cookies don't stay together. I use a kitchen scale and a tablespoon to mine and weigh the dough, arranging them into 3 x 4 grids on two big cookie sheets. Space them out ... the dough melts and spreads, so you don't want them running into each other.
The cook time says 12-14 minutes, but that's for smaller cookies than what I'm making here. Start watching after 15-16 minutes so they don't burn, but cook time will be closer to 20 minutes.
Remove the cookie sheets from the oven. This may not be at the same time ... for whatever reason, the upper cookie sheet always seems to be ready before the lower one.
Let the cookie sheets cool for 5-6 minutes (don't rush it, or else the cookies just fall apart when you try to move them) then carefully twist and move each cookie to a wire rack to finish cooling.