To the bowl of a stand mixer fitted with the paddle attachment (or large mixing bowl and electric mixer) combine the egg, butter, sugars, vanilla, and beat on medium-high speed until creamed and well combined, about 4 minutes.

Stop, scrape down the sides of the bowl, and add the oats, flour, cinnamon, baking soda, optional salt, and beat on low speed until just combined, about 1 minute.

Stop, scrape down the sides of the bowl, and add the chocolate chips, optional raisins or nuts, and beat on low speed until just combined, about 30 seconds.

Using a large cookie scoop, 1/4-cup measure, or your hands, form approximately 11 equal-sized mounds of dough, roll into balls, and flatten slightly. Tip – Strategically place a few chocolate chips on top of each mound of dough by taking chips from the underside and adding them on top.

Place mounds on a large plate or tray, cover with plastic wrap, and refrigerate for at least 2 hours, up to 5 days. Do not bake with unchilled dough because cookies will bake thinner, flatter, and be more prone to spreading.

Preheat oven to 350°F (175°C), line a baking sheet with a Silpat or spray with cooking spray. Place dough mounds on baking sheet, spaced at least 2 inches apart (I bake 8 cookies per sheet).

Bake for about 11 minutes (for super soft cookies, longer for more well-done cookies), or until edges have set and tops are just set, even if slightly undercooked, pale, and glossy in the center; don’t overbake. Cookies firm up as they cool.

Allow cookies to cool on baking sheet for about 10 minutes before serving. I let them cool on the baking sheet and don’t use a rack.