Preheat oven to 350F (175C) and lightly grease and flour a bundt pan. Set aside.
In KitchenAid mixer, or with electric mixer in large bowl, cream together butter and cream cheese.
Beat in sugars until light and fluffy.
Add eggs, one at a time, beating until combined. Scrape down sides and bottom of mixing bowl with rubber spatula.
Stir in vanilla extract.
In separate, medium-sized bowl, whisk together flour, baking powder, cornstarch and salt.
Gradually add flour mixture to wet mixture, alternating with buttermilk, until all of the flour mixture and buttermilk have been combined. Batter will be thick.
Fold in cranberries (do this by hand, as the mixer may squish the berries)
Evenly spread batter into prepared bundt pan. Bake on 350F (175C) for 55 minutes, or until a toothpick inserted in the center of the cake (preferably in a crack) comes out mostly clean with no wet batter.
Allow cake to cool in the bundt pan for 15 minutes before carefully inverting onto a cooling rack to cool completely. Allow cake to cool completely before adding white chocolate.
White Chocolate Glaze
Combine heavy cream and white chocolate chips in a small saucepan over low heat.
Stir frequently until chocolate has melted and mixture is smooth. Remove from heat and allow to cool for 10-15 minutes (if you pour it right away the glaze will be extremely thin and will mostly slide right off your cake), stirring occasionally, before pouring over your completely cooled bundt cake.
Allow glaze to set before cutting and serving.