Melt 1 stick of butter in a small saucepan over medium heat.  It will melt, separate into milk solids and clear butter, foam and then start browning.  It will take a lot longer than you think it will, but do not venture far and stir often, because once it starts to brown, it will go quickly.  Once the butter is browned and smells nutty, it is ready.  Cool slightly.

In the bowl of a stand mixer fitted with the paddle attachment, cream the remaining stick of butter and cream cheese until completely combined, light and creamy.  Add the cooled browned butter and brown and white sugars, and cream together until light and fluffy.  Add the eggs and vanilla extract and beat on medium-low speed until pale and fluffy, about 3 minutes.

In a medium bowl, combine the flour, milk powder, baking soda, baking powder and salt and whisk to combine.  Add the dry ingredients into the creamed mixture and mix until just combined.  Fold in the macadamia nuts and white chocolate by hand.  Cover the bowl with plastic wrap and refrigerate until chilled, at least 1 hour.

Preheat the oven to 350°.  Line two baking sheets with parchment paper.  Using an ice cream scoop, spoon the cookie dough into balls (about 2 tablespoons each) and place on the prepared cookie sheets.  Using a glass, slightly flatten the dough balls, flouring the glass if necessary to prevent sticking.  Leave about 1-1/2 inches between each cookie to allow them to spread.  Bake for 11 to 13 minutes, until the edges begin to brown but the middle is still soft.  Allow to sit on cookie sheets for 2 minutes once removed from the oven before transferring to cooling racks.