Beat butter until smooth (I use a stand mixer but a hand mixer will work too). Add sugar and beat until fluffy. Beat in vanilla extract and eggs (one at a time) until incorporated.
Add flour, baking soda, salt to the bowl and beat until just combined. Stir in oats and raisins.
I skip chilling but you can chill for an hour and have better results.
Preheat oven to 375F and line two baking sheets with parchment.
Scoop balls onto the sheet, flatten and sprinkle with (optional) coarse sea salt.
Bake cookies until golden at the edges, about 12 minutes.
Notes
Keep cookies refrigerated or frozen and let them come to room temperature before enjoying.