Preheat oven to 350°F (175°C) and line two baking sheets with parchment. Brown half the butter in a saucepan until nutty and golden, about 4–5 minutes; pour into a large bowl to cool.

Add the remaining butter and both sugars to the browned butter. Cream on medium speed until light and fluffy, about 2 minutes. Beat in the egg and vanilla until smooth.

Whisk together the flour, baking soda, and salt. Mix into the butter mixture on low in two batches, just until combined. Fold in the oats, white chocolate chips, and dried cranberries with a spatula.

Scoop dough onto the sheets, spacing 2 inches apart. Bake one sheet at a time on the center rack for 10–12 minutes, until edges are golden and centers look slightly underdone.

Let cookies rest on the sheet for 5 minutes, then transfer to a wire rack. Serve warm or let cool completely.