1. In the bowl of a stand mixer, beat the butter and sugars until very light and fluffy, about 5 minutes.
2. Meanwhile in a separate bowl, whisk together the flour, baking soda, salt, nutmeg, and cinnamon, making sure there are no lumps of baking soda. Stir in the oats and raisins.
3. Add the eggs, one at a time, and beat until thoroughly combined. On low speed, or by hand, gradually add the flour and oat mixture to the creamed butter, mixing until completely incorporated.
4. Chill the batter a few hours or overnight, covered. (This step is optional, although recommended by the author.)
5. To bake the cookies, preheat the oven to 350ºF (180ºC). Line a baking sheet with parchment paper or a silicone baking mat.
6. Drop the dough in 1/4 cup (50 g) balls evenly spaced on the baking sheet and flatten the tops slightly with your hand.
(I got about 8 cookies per baking sheet.)
7. Midway during baking, rotate the baking sheet and tap the tops of the cookies down somewhat firmly with a spatula to flatten the domes.
8. Bake the cookies for 20 to 22 minutes, until they just start to turn brown across the top, but do not overbake.
Remove from oven and cool completely.