Start by soaking the raisins in hot water for about 10 to 15 minutes. This simple step will plump them up and enhance their natural sweetness. Drain the raisins and set them aside.
Preheat your oven to 350°F (175°C). This ensures that your cookies bake evenly and come out perfectly golden.
In a large bowl, whisk together the all-purpose flour, ground cinnamon, baking soda, and fine sea salt. This step helps to evenly distribute the leavening agents and spices.
In another bowl, use an electric mixer to cream together the slightly softened unsalted butter, light brown sugar, and granulated sugar until the mixture is light and fluffy. This should take about 2-3 minutes.
Beat in the egg and vanilla extract to the butter-sugar mixture until well combined. The mixture should look smooth and creamy.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix, as this can lead to tough cookies.
Fold in the old-fashioned oats and the soaked raisins. Make sure they are evenly distributed throughout the dough.
Using a cookie scoop or tablespoon, drop heaping tablespoons of dough onto a baking sheet lined with parchment paper, leaving enough space between each cookie for spreading.
Place the baking sheet in the preheated oven and bake for 10-12 minutes, or until the edges are golden brown. The centers may look a bit underbaked, but they will continue to firm up as they cool.
Remove the cookies from the oven and let them cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Enjoy the warm, comforting aroma of fresh cookies filling your kitchen!