1. Make cake: Preheat oven to 350°F. Butter and flour a 10-cup nonstick Bundt pan. Sift 3 cups flour, baking powder and salt into a bowl. In a separate bowl, toss candies with remaining 1/2 cup flour.
2. Using an electric mixer on medium-high speed, beat butter and sugar until light, 3 minutes. Add yolks one at a time. Beat in vanilla. Beat in 1/3 of flour mixture, followed by 1/2 of milk. Repeat, ending with flour mixture. Do not overmix.
3. In a clean, dry bowl using dry beaters, beat egg whites and cream of tartar until stiff peaks form. Stir candies and 1/3 of egg whites into batter. Fold in remaining whites. Spoon batter into Bundt pan. Bake until a toothpick inserted into center comes out clean, 50 to 60 minutes. Let cool on a wire rack for 10 minutes, then unmold cake.
4. Make icing: Place chocolate in a bowl. Warm cream in a pan over medium heat until just boiling. Pour over chocolate, let stand for 1 minute, then whisk until smooth. Let cool slightly. Pour icing over cake, allowing excess to drip over sides.