Begin by preparing your baking area. Preheat your oven to 350°F (175°C) and line your baking sheet with parchment paper or use a silicone baking mat. This ensures your cookies won’t stick.
In a large mixing bowl, combine the softened butter, egg, brown sugar, and vanilla extract. Using a stand mixer fitted with a paddle attachment, beat these ingredients together on medium-high speed until they are light and fluffy. This should take around 4 to 5 minutes. Make sure to scrape down the sides of the bowl to incorporate everything evenly.
Next, add in the oats, ground cinnamon, baking soda, and optional salt to the mixture. Beat these ingredients on low speed until just combined, about 1 minute. Don't overmix at this stage; we want to maintain that chewy texture.
Now, it's time to add the bread flour. Slowly pour it into the bowl and beat on low speed until just incorporated, around 30 seconds. The dough will be thick, which is exactly what we want for these cookies.
Finally, add in the raisins and mix for a few seconds to combine. This will distribute the raisins throughout the dough.
Once your dough is ready, transfer it to an airtight container or cover the mixing bowl with plastic wrap. Refrigerate the dough for at least 2 hours, or up to 5 days. This chilling process is crucial, as it helps the cookies maintain their shape during baking.
After the chilling period, scoop the dough using a medium-sized cookie scoop, which is about two heaping tablespoons or around 1.50 to 1.60 ounces by weight. Form mounds and place them on your prepared baking sheet, spacing them at least 2 inches apart. Aim for a maximum of 8 per sheet to give them room to spread.
Pop the baking sheet into your preheated oven and bake for 10 to 12 minutes. Keep an eye on them; you want the edges to be set while the tops remain slightly undercooked. This ensures a soft and chewy center.
Once they are out of the oven, let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. This resting time allows them to firm up.