Beat the butter, sugar, brown sugar, and vanilla in a large mixing bowl until fluffy and smooth.
Add the eggs one at a time, mixing after each addition.
Combine the flour, baking powder, salt, and cinnamon in a medium mixing bowl. Add the dry ingredients to the wet ingredients in two additions, mix until just combined after each addition.
Use a wooden spoon or rubber spatula to stir in oats, pistachios, and craisins.
Portion the cookie dough into 2 tablespoon balls and place 2 inches apart on a greased or silicone mat-lined baking sheet.
Bake for 12-14 minutes or until the cookies are golden and set. Remove from the oven and transfer to a wire rack to cool. Repeat with the remaining cookie dough.
Once the cookies are cooled, spread some melted white chocolate on the bottom of each cookie and set them on the wire racks upside down to let the chocolate set up.