Preheat oven to 180 degrees C and place rack in center of oven. Butter and dust a 10 inch bundt pan with flour and dust off excess flour..

In a heatproof bowl, placed over a saucepan of simmering water, melt the chocolate with the coffee. Remove from heat and set aside to cool to room temperature.

In a separate bowl, sift or whisk together the flour, baking powder, baking soda, and salt.Keep this aside

Beat the butter until smooth with a hand mixer or using electric mixer. Gradually add the sugar and continue to beat until the mixture is light and fluffy (about 3-5 minutes). Scrape down the sides of the bowl as needed. Add eggs, one at a time, beating well after each addition. Beat in the vanilla extract and Yohurt.

With the mixer on low speed, alternately add the flour mixture and the milk to the batter, in three additions, beginning and ending with the flour. Remove a little more than half of the batter and place into a separate bowl. To the remaining batter stir, or beat, in the melted chocolate. Place the batters into the prepared bundt pan by alternating spoonfuls of vanilla batter with the chocolate batter. Then, with the end of a wooden skewer or knife, gently draw swirls through the batter to marbleize it. Don’t over mix.