1. Preheat oven to 325 degrees F. Line baking/cookie sheet with parchment paper. In a mixer on medium speed, mix butter, sugars, vanilla & Nutella until smooth, about 1 minute.
2. Add egg & egg yolk and mix again until blended. In a large bowl, whisk flour, baking powder, baking soda & salt until combined well. Slowly add flour mixture to butter/Nutella mixture, beating on low speed until incorporated well.
3. Add chocolate chips last, stirring with a large spoon to evenly distribute throughout dough.
4. Place batter onto cookie sheet using a cookie scoop, or by level tablespoons. Using the back of a spoon, flatten dough.
5. Bake for approximately 14 minutes, or until edges of cookies are browned. Cool on the cookie sheet & transfer to a wire rack. Store in an airtight container.