Preheat your oven to 375 degrees and line a baking sheet with parchment paper or a non-stick silicone baking mat. Set aside.
In a medium sized bowl combine your dry ingredients together; flour, pudding mix, baking soda, baking powder and salt.
In a large bowl using electric beaters (or a stand mixer) cream together butter, white sugar, and brown sugar. Do this for about 2 minutes until smooth.
Now, add in the egg, egg yolk, and vanilla. Mix until just combined.
Slowly add your dry ingredients (flour mixture) to the wet ingredients (butter and sugar mixture) and beat until mixed well.
Then, fold in your white chocolate chips. Your dough will be firm- this is good!
Using a cookie scoop or a spoon take ~2 tbsp of cookie dough and form it into a ball, place it on the baking sheet and slightly flatten it. Repeat with remaining cookie dough, leaving ~2 inches of space between the cookies.
Bake your cookies for 8-9 minutes (8 minutes for chewier cookies and 9 minutes for crispier ones!). Allow to cool fully and enjoy!