Add sugar and egg yolk to a mixer bowl and beat on high speed for a few minutes. Then start adding butter (one tablespoon at a time) and beat for a few more minutes. Remove from the mixer bowl and wash the bowl.
Add flour, baking powder, and vanilla sugar to another large bowl. Mix until combined.
Add egg whites and beat on high speed for a few minutes until foamy in a mixer bowl.
Add egg whites to the egg yolk mixture and gently fold with a spatula.
Add the egg mixture to the bowl with flour, baking flour, and vanilla sugar. Add 4 tablespoon of milk. Mix until combined (don't overmix). Divide into two equal parts.
Melt 1 tablespoon unsalted butter and chocolate in a small bowl on medium heat. Set aside for a few minutes before adding it to one of the batter parts. Mix until combined.
Combine the dried cranberries and dried apricots and add half of the mixture to each batter part.
Preheat the oven to 350 Fahrenheit. Grease the bundt pans with butter and dust with flour. Shake off any excess flour.
Fill each bundt pan with batter (you can use the batter with the chocolate or without it.)
Bake for 28 minutes or until the toothpick comes out clean. Note that muffins will take longer to bake (if using muffin pan).
While the bundt cakes are baking, prepare the sugar icing. Add powdered sugar, half-and-half, vanilla extract, lemon juice, and food coloring in a medium-size bowl. Mix until combined. Feel free to add any food color you prefer – I decided to go with something for Valentine's Day (deep purple and pink).
Pour the icing on each mini bundt cake (or muffin) and sprinkle decorations on top. Enjoy!
Notes
This recipe can yield one large bundt cake, 24 mini bundt cakes, 12 mini bundt cakes, and 9 muffins or 18 muffins. Please note the bake time might vary.
To create the beautiful mini marble bundt cakes, add batter with chocolate and batter without it (alternately). Then gently swirl the batter with a knife.