Preheat your oven to 350°F (175°C).
In a bowl, whisk together oats, flour, baking soda, cinnamon, and salt.
In a separate bowl, cream together butter and brown sugar until smooth.
Add in the egg and vanilla, mixing well.
Gradually add dry ingredients to the wet ingredients, stirring until combined.
Stir in raisins to ensure they're evenly distributed.
Scoop dough onto a baking sheet, spacing cookies 2 inches apart.
Bake for 10-12 minutes until golden brown and set.
While cookies bake, make the espresso dipping sauce.
In a saucepan, heat brewed espresso, heavy cream, and brown sugar over medium heat.
Stir frequently, allowing the sauce to thicken slightly.
Once thickened, remove from heat and stir in vanilla.
Let the sauce cool slightly, then serve with warm cookies for dipping.