In a large mixing bowl, beat together the egg, softened butter, packed light brown sugar, granulated sugar, and vanilla extract until light and fluffy.

Gradually add the rolled oats, flour, ground cinnamon, baking soda, and pinch of salt to the creamed mixture.

Gently stir in the semi-sweet chocolate chips and fold in raisins or nuts if using.

Scoop the dough into mounds, cover with plastic wrap, and refrigerate for at least 2 hours.

Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

Bake the chilled dough mounds in the preheated oven for approximately 11 minutes.

Allow the cookies to cool on the baking sheet for about 10 minutes before transferring them to a wire rack.