Place yeast, warm milk and sugar and ½ cup of flour in a mixing bowl and mix until dissolved. Cover and set aside for 15 min in a warm spot in the kitchen.
Place raisins in a small bowl, add water (or alcohol) and soak for 10 minutes. Melt butter and set aside to cool.
Place raisins in a strainer and add corn starch. Shake it around to cover raisins and get rid of excess corn starch.
After 15 minutes of yeast mixture proofing, add raisins, remaining flour, butter, egg, egg yolks, vanilla extract, lemon zest, and salt and mix to form dough. Transfer onto a clean, floured surface and knead for no less than 15 minutes. Add another tablespoon of flour if dough is too wet.
Grease bundt pan with butter, place dough in pan, distribute evenly. Cover with a towel and set aside for at least 2 hours in a warm spot. The dough has to (at least) DOUBLE in size.
Preheat oven to 350°F / 180°C. Place babka in the middle rack and bake for 40–45 minutes. When done, let rest for a few minutes and then transfer to a cooling rack.
To make icing, place powdered sugar in a small mix- ing bowl. Add a few drops of lemon juice and keep adding 1 teaspoon of hot water at a time. Mix until combined; it should create a paste. Adjust the amount of water and sugar for the desired thickness of the icing. Pour over cake once cake has cooled off.
