Add both sugars and beat together at medium-high speed for 3-4 minutes until light and fluffy. Scrape down paddle, sides and bottom of the bowl as needed.
Reduce speed, add the egg and mix at medium speed until incorporated.
Add the vanilla and maple syrup and mix until combined.
Fold in the dry ingredients (see point 1) and mix now with a rubber spatula until just combined.
Fold in the white chocolate chips and pistachios and mix until totally incorporated. (Dough will be thick and sticky at this point.)
Chill the dough for 25-30 minutes in the refrigerator.
Line two* large cookie sheets with parchment paper or silicone baking mats. Set aside.
Roll balls of dough (about 1 - 1½ tablespoons of dough per cookie) and place them 2 inches apart on the cookie sheets. You can either shape your cookie dough balls using your hands (remember, it will be rather sticky) or you can also use a small ice cream scoop. (If you feel like it, you can press a few extra chocolate chips/chopped pistachios on top of the cookies so that they are more visible after baking.)
Bake for 12-14 minutes until they appear slightly brown around the edges but the center is still soft. Do not over bake; these cookies are very soft and fragile while hot, but their consistency will become firmer when cooled.
Remove from the oven and let cool on baking sheet for 5 minutes before transferring to a cooling rack to let cool completely.Cover cookies and store at room temperature for up to 1 week.
Notes
- *In case you only have one cookie sheet, keep cookie dough in the refrigerator between batches and do not bake a new batch of cookies until the cookie sheet is completely cold. - Baked cookies and rolled cookie dough freeze well, up to 3 months.
Recipe by Pemberley Cup & Cakes at https://pemberleycupandcakes.com/en/2014/11/18/white-chocolate-pistachio-oatmeal-cookies/