Start by adding the raisins to a medium mixing bowl and covering them in hot water. Let them soak for at least 10 minutes or until they've softened. Drain the water and pat the raisins dry.
While the raisins are soaking, brown the butter. You’ll start by melting the butter over medium heat in the pan. Once melted, constantly whisk the butter, and continue to cook it until it reaches a rich, golden color. This can burn very easily so be sure to keep a close eye on it. You’ll know it’s done when the surface is foaming, the underneath is browned, and it smells very toasty and nutty. When it reaches this point, immediately remove it from the heat and set aside to cool.
In a large mixing bowl, combine the wet ingredients. This includes the cooled brown butter, brown sugar, eggs and vanilla extract. Whisk until smooth!
Sprinkle the flour, oats, baking soda and cinnamon into the wet ingredients and mix to combine. Lastly, fold in the soaked and drained raisins.
Let the dough sit in the fridge for 30 minutes while the oven preheats to 350 degrees F.
Scoop or roll the cookies into 2-inch balls and place them on parchment lined baking sheets. Bake for 14 minutes or until the edges are lightly brown. Let them set up for 5 minutes on the baking sheets before enjoying!