Preheat your oven to 350°F (175°C).
In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt. Add the softened butter, milk, eggs, and vanilla extract. Mix until just combined.
Gently fold in the chopped cranberries and white chocolate chips into the batter.
Pour the batter into your prepared 9x13-inch baking pan and spread it evenly. Bake for 30-35 minutes, checking for doneness with a toothpick.
While the cake is baking, prepare the glaze by whisking together the powdered sugar, milk, and vanilla extract until smooth.
Allow the cake to cool in the pan for about 10 minutes, then transfer it to a wire rack. Drizzle the glaze over the top while the cake is still warm.