Step 1: Preheat your oven to 375°F (190°C). Line baking sheets with parchment paper or silicone mats.
Step 2: In a large bowl, cream together the softened butter, granulated sugar, and packed brown sugar until light and fluffy.
Step 3: Beat in the large egg and orange juice until well combined.
Step 4: In a separate bowl, whisk together the all-purpose flour, baking powder, salt, and baking soda.
Step 5: Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix.
Step 6: Gently fold in the chopped fresh or frozen cranberries and chopped walnuts until evenly distributed throughout the dough.
Step 7: Drop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.
Step 8: Bake for 10-12 minutes, or until the edges are lightly golden and the centers are set. Transfer cookies to a wire rack to cool completely.
Step 9: While cookies cool, prepare the frosting: In a medium bowl, beat 1/3 cup softened butter until creamy. Gradually add the confectioners' sugar, vanilla extract, and 2 tablespoons of hot water, beating until smooth and spreadable. Add more hot water, 1 tablespoon at a time, if a thinner consistency is desired.
Step 10: Once the cookies are completely cool, spread a generous amount of frosting on each cookie. Allow the frosting to set slightly before serving or storing.