Preheat oven to 350 degrees. Line a baking sheet with parchment paper.
Whisk flour, baking powder,baking soda and table salt in a medium bowl.
In a mixer beat butter and sugars until light and fluffy.
Scrape down bowl with rubber spatula then add egg and vanilla and beat until incorporated.
Scrape down bowl again.
Add flour mixture gradually and mix until just incorporated and smooth.
Gradually add oats and white chocolate and mix until incorporated.
Divide dough into 24 equal portions, about 2 tablespoons eac. Roll between palms into balls, then place on lined baking sheet 21/2 inches apart. Using fingertips, gently press down each ball to about 3/4 inch thickness.
Sprinkle a flake or two of sea salt on each cookie.
Bake until cookies are deep golden brown, 13-16 minutes.