Heat oven to 350°F. Line a 9x13" pan with a parchment paper sling.
Cream butter and brown sugar together in the bowl of a stand mixer. Beat in eggs and vanilla.
1/2 cup salted butter, 1 1/2 cups light brown sugar, 2 large eggs, 1 teaspoon pure vanilla extract
Whisk together the flour, baking powder, and salt in another bowl, then add to the butter and sugar mixture, stirring just until combined.
1 1/2 cups all-purpose flour, 1 teaspoon baking powder, 1/4 teaspoon salt
Stir in the cranberries, 1 cup of the white chocolate, and pecans, then spread into the prepared 9x13" pan. Bake for 30-35 minutes, until golden brown. Do not overbake.
1 1/2 cups white chocolate chips, 2 cups fresh or frozen cranberries, 1/2 cup pecans
Cool completely, then cut into individual bars or triangles. Melt the remaining 1/2 cup of white chocolate in the microwave in short 20 second bursts, stirring well between each burst of heat until melted. Transfer to a plastic bag, snip off the corner, and drizzle over the cooled bars. Let set before serving.