Preheat the oven to 350F (177C) convection OR 325F (163C) conventional and line two cookie sheets with parchment paper.
In a medium bowl, microwave the butter for 20-30 seconds, just until it's melted (if it gets super hot, then let it cool a little bit).
1/4 cup (56 g) salted butter
Add the light brown sugar to the melted butter and whisk together for about a minute. Add in the egg and vanilla and whisk until it's completely smooth.
2/3 cup (132 g) light brown sugar, 1 large egg, 1 tsp vanilla extract
Add the flour, oatmeal, cinnamon, baking powder and salt and fold the cookie dough just until there are no more steaks of flour left.
3/4 cup (90 g) all-purpose flour, 3/4 cup (80g) old fashioned rolled oats, 1/2 tsp ground cinnamon, 1 tsp baking powder, 1/4 tsp fine sea salt
Fold in the raisins and white chocolate, just until they're evenly dispersed.
1/4 cup (2oz) raisins, 1/2 cup (3 oz) white chocolate chips
Split cookie dough into 8 cookies, about 2.5 ounces each, placing 4-6 per cookie sheet. Bake one sheet on the middle rack for 12-14 minutes, just until the edges are starting to brown and the center is puffed.
Remove them from the oven, give the pan a quick tap on the counter and use a biscuit cutter to scoot the cookies to make them round (if desired).
Sprinkle with sea salt flakes and allow them to rest for 5-10 minutes before transferring off the cookie sheet.
tiny pinch sea salt flakes