Preheat oven to 375°F. Line baking sheets with parchment paper or silicone baking mats.

Pour enough hot water over the raisins to cover them and let them sit for 10-15 minutes, then drain before use.

In a bowl, whisk together flour, cornstarch, baking soda, salt, and cinnamon; set aside.

Using a hand mixer or a stand mixer fitted with a paddle attachment, beat the butter for 30 seconds. Add sugars and beat until light and fluffy. Add eggs, one at a time, beating until combined. Stir in vanilla extract. Scrape down the sides and bottom of the bowl as needed.

Gradually add flour mixture to butter mixture until thoroughly combined. Slowly stir in oats and raisins until completely combined.

If desired, chill dough in the refrigerator for 30 minutes.

With a medium cookie scoop (1 1/2 Tablespoons), portion out the cookie dough. Place 2 inches apart on the baking sheet.

Bake for 10-13 minutes or until very lightly browned on the sides. The centers will look very soft. Remove from the oven and let cool on the baking sheet for 5 minutes before transferring to a wire rack to completely cool.