Prep Your Ingredients
Measure out all your ingredients before you start mixing. Ensure your cold butter is cut into small cubes for easier creaming.

Cream Wet Ingredients
In a large mixing bowl, combine the cold, cubed butter with both the brown sugar and granulated sugar. Cream the mixture together until it becomes light and fluffy, indicating air has been incorporated. Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract. Scrape down the sides of the bowl with a spatula to ensure all ingredients are thoroughly combined.

Combine Dry Ingredients
In a separate medium bowl, whisk together the all-purpose flour, rolled oats, baking soda, cornstarch, and salt. This step is crucial for ensuring that the leavening agents and other dry ingredients are evenly distributed throughout the dough.

Mix Wet and Dry
Gradually add the whisked dry ingredients to the creamed wet ingredients. Mix on low speed just until the ingredients are combined. Be careful not to overmix, as this can develop the gluten in the flour and lead to tough cookies.

Fold in Cranberries and White Chocolate Chips
Using a spatula, gently fold in the sweetened dried cranberries and white chocolate chips. This gentle folding motion helps to distribute them evenly throughout the dough without overworking it.

Scoop and Bake
Drop spoonfuls of the cookie dough onto a baking sheet lined with parchment paper, making sure to leave enough space between each cookie for them to spread as they bake. Bake in a preheated oven (usually 375°F or 190°C) until the edges of the cookies are golden brown but the centers still look soft. They will continue to set as they cool.