Preheat the oven to 350°F (175°C or 180°C) and line 2 sheet pans with parchment paper. Pulse the fresh cranberries in a food processor about 6 or 7 times, until chopped to the size you like. Measure 2 cups after chopping.
Juice an orange to get at least 2 tablespoons of fresh juice. If your walnuts are not already chopped, chop enough to measure 1 cup.
Weigh or measure the white sugar and light brown sugar into a bowl and set it aside. In a separate bowl, weigh or measure the flour. Add the baking powder, baking soda, and salt, then whisk to blend.
Cube the room temperature butter into the mixer bowl and cream on medium speed for about 1 minute. Scrape down the bowl, then add both sugars and mix on medium speed for 3 minutes. The mixture will still look grainy because there is more sugar than butter.
Add the egg, milk, and orange juice. Mix on medium-high speed for about 1 to 2 minutes, until fairly smooth. Scrape down the sides of the bowl.
Turn the mixer to low speed and add the flour mixture about a third at a time. Mix just until incorporated, scraping down the bowl as needed. Remove the bowl from the mixer and use a spatula to stir in the chopped cranberries by hand, then the chopped walnuts. This keeps the mixer from breaking the cranberries into smaller pieces.
Use a medium cookie scoop to place 12 scoops of dough onto a parchment-lined sheet pan. Bake 1 sheet pan at a time at 350°F (175°C or 180°C) for 12 to 14 minutes. Let the cookies rest on the pan for 1 minute before moving them to a cooling rack. Cool completely before frosting.