Preheat the oven to 375°F. Line a baking sheet with parchment paper.
In a large bowl, whisk together 1/2 cup all-purpose flour, 1/4 tsp salt, and 1/4 tsp baking soda. Set aside.
Melt 3 tbsp unsalted butter in a skillet over medium heat, swirling the pan occasionally. Continue to cook until the liquid is golden brown and has a nutty aroma, 1 to 2 minutes. Immediately transfer the butter to a large bowl.
In the same bowl, stir in 1 tbsp vegetable oil, 1/4 cup brown sugar, and 1/8 cup granulated sugar. Whisk until well combined.
Add 1 egg, 1/2 tsp vanilla extract, and 1/8 tsp ground cinnamon, use a spatula to whisk until the mixture is smooth. Stir in the flour mixture until fully incorporated, about 1 minute. Then add 4 oz old-fashioned rolled oats and 1/4 cup raisins, and mix until combined. The mixture should be a little stiff.
Divide dough into 20 portions, each about 1 tablespoon. Arrange dough balls on the prepared baking sheet. Use your hands to press the dough balls into 2-inch disks. Let the dough balls chill in the refrigerator for at least 5 minutes before baking.
Bake for 8-10 minutes or until cookie edges are set and lightly browned while the center is still soft. Let the cookies cool on the sheet for 5 minutes. Then transfer them to a dish and let cool completely.
Serve: Take the cookies out of the oven and let them cool on the sheet for 5 minutes. Then transfer them to a dish and let cool completely.