Preheat the over to 180º C / 350º F.

Butter a loaf pan, from the bottom up the sides.
Dust with flour, and
Turn the loaf pan upside down on the counter.
Pat it several times to remove the excess flour.
Set the mold aside in the refrigerator.

Melt the chocolate, cut into pieces,
In a bain-marie.
Once completely melted and shiny,
Set aside and cool.

Beat together the butter and the sugar.
Once well blended,
Incorporate the eggs, one by one.

Flavor with a scraped vanilla bean.

Add the flour and the baking powder,
Then the melted chocolate, and finally,
The yogurt.
Beat vigorously,
But not too long!

For a pleasant change,
Prepare a mixture of raisins, crushed walnuts, and
Half of the sugar.
In this case, use the other half of the sugar
For the butter/sugar mixture.

Pour one half of the dough into the buttered loaf pan.
Incorporate the raisin and walnut mixture, and
Top with the remaining dough!

Bake.