Soak the raisins in warm water or diluted rum and water mixture. Let sit while you prep the cookie dough.
Make the flax egg. Combine 1 TBSP ground flax seeds with 3 TBSP water and thicken in the fridge for 10 minutes.
In a large bowl, combine white and brown sugars.
In a medium bowl, whisk flour, oats, cinnamon, baking soda, and salt.
Brown the butter: (see photos above) add the butter to a nonstick pan and heat on medium-low, stirring occasionally, for about 5 minutes or until desired brown hue is achieved. The butter will froth (especially if you use mykonos), whenever this happens, lift the saucepan off the burner and wait for the frothing to subside while swirling gently. Put the pan back on the burner and continue to cook, pulling pan on and off the burner, until butter is golden brown.
Add the browned butter to the sugars. Whisk to combine. Add the vanilla, flax egg, molasses, and applesauce. Whisk some more.
Fold in the dry ingredients until almost combined.
Dry the soaked raisins with a dishcloth or paper towel. Add them to the dough, folding gently to combine.
Refrigerate: cover the dough and chill for at least 2 hours, but ideally 9-24 hours.
Bake: preheat the oven to 350℉. Line a light-colored baking tray with parchment paper or a silpat mat. Scoop the cold dough into balls about 2.5 tbsp each. Allow 2-3" between each on the tray - they'll expand while baking. Bake for 11 minutes or until edges darken slightly.
Cool on the baking tray for 10 minutes (see expert tips for optional shaping step!), then transfer to a wire cooling rack to cool completely.