Preheat the oven to 350 F. Grease and line a pullman loaf pan with parchment paper. If not using a pullman you can make two shorter loaves or one loaf and some muffins.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter, sugar, baking powder and soda and salt for at least 5 minutes - until very light and fluffy.

Add the eggs and yolk and beat for another 3 minutes, scraping down as needed, batter should be very smooth.

Add the ground nuts, flour and cocoa and mix it in with a spatula (to avoid dry ingredients making a mess).

With the mixer on, pour in the kefir. Scrape the bowl as needed and run the mixer until you have a smooth batter.

Pour the batter into the prepared ban(s).

Bake for 65-75 minutes for the pullman loaf. If using a standard-size loaf pan, check the cake at the 50 minute mark. In both cases the cake is done when pressed at the top and it springs back (or use a cake tester).

Let the cake cool for a few minutes in the pan then turn it onto a cooling rack.

Once it’s completely cool make the glaze: whisk all the ingredients together in a bowl. Add more heavy cream if it’s very thick, add more powdered sugar if it’s too loose. Try to get the consistency of spreadable but not overly drippy.