1/2 cup (1 stick or 4 ounces) butter, softened
2/3 cup light brown sugar, packed
1/2 teaspoon vanilla extract
3/4 cup all-purpose flour
1/2 teaspoon baking soda
1/2 teaspoon ground cinnamon
1/4 teaspoon salt (I often use a half teaspoon, but I like more salt in my baked goods)
1 1/2 cups rolled oats
3/4 cup raisins
1/2 cup walnuts, chopped (optional)
Preheat oven to 350°F (175°C).
In a large bowl, cream together the butter, brown sugar, egg and vanilla until smooth. In a separate bowl, whisk the flour, baking soda, cinnamon and salt together. Stir this into the butter/sugar mixture. Stir in the oats, raisins and walnuts, if using them.
At this point you can either chill the dough for a bit in the fridge and then scoop it, or scoop the cookies onto a sheet and then chill the whole tray before baking them. You could also bake them right away, if you're impatient, but I do find that they end up slighly less thick.
The cookies should be two inches apart on a parchment-lined baking sheet. Bake them for 10 to 12 minutes (your baking time will vary, depending on your oven and how cold the cookies were going in), taking them out when golden at the edges but still a little undercooked-looking on top. Let them sit on the hot baking sheet for five minutes before transferring them to a rack to cool.