Preheat oven to 350 degrees and line baking sheets with parchment paper. 

In a bowl, beat the butter and sugars on medium high until they're light and fluffy.

In another bowl, combine the flour, baking powder, baking soda, and salt. 

Once the butter and sugar is fluffy, add the egg and the vanilla continuing to beat. 

With the mixer on slow, gradually add the flour mixture to the butter/sugar mixture until combined.

Slowly add the oats in 1/2 cup increments. Make sure to scrape down the inside of the bowl with a spatula and mix on slow until combined. Add white chocolate chips. 

Form the dough into 28 equal balls and arrange on the baking sheet. Leave lots of space in between them. Use your fingers to mash down the dough balls to be about 1/2" thick discs.

Place cookie sheet on the middle rack and bake for about 15 minutes or until the edges are lightly browned. Remove the pan from the oven and place on a cooling rack. Allow cookies to cool on the cookie sheet. 

Enjoy.