Bring a little water to a boil in a small saucepan and throw in the raisins.
Turn off the heat and let it sit for 2 minutes, then drain the raisins.

Put the yeast and milk in the mixer bowl and, using a wooden spoon, stir until the yeast is dissolved.
Add the flour and salt and mix just enough to moisten the flour.

In a small bowl, lightly beat the eggs and egg yolk with a fork.
Put the dough hook on the mixer, and working at low speed, pour in the beaten eggs, mix until they are incorporated.
Add the sugar, then increase the speed to medium-high, and beat until the dough forms a ball, about 5 minutes.
Reduce the mixer speed to medium and add the butter, taking care that each piece is incorporated before adding another.

Increase the mixer to medium speed and beat until the dough is soft and elastic, about 10 minutes.
Remove the bowl from the mixer and incorporate the raisins.
Put the dough in a clean bowl, cover it with plastic wrap, and let it sit in a warm place until it has almost doubled in volume, about 1 and 1/2 hours.

Deflate the dough by lifting it on the edges and letting it drop back into the bowl.
Cover the bowl again and put it in the refrigerator.
Repeat this process every 30 minutes for 2 hours.
Let the dough rest in the refrigerator overnight.

Divide the dough into 12 small molds for individual bundt cakes, cover with greased parchment paper, and let it rise for 2 to 3 hours.

When the dough has risen about 1″ (2.5 cm) above the mold, preheat the oven to 375 F (190 C).

Remove the parchment paper and bake the kougelhopfs for 10 minutes.
Cover them with aluminum foil and continue baking for an additional 15 minutes.

Remove the cakes from the oven and transfer them to a rack.
Brush them with melted butter.

Just before serving, dust with powdered sugar.