In a large bowl or stand mixer, cream butter and sugar. Add mashed bananas, eggs and yogurt. Mix until barely combined. Add dry ingredients. Mix well.

Melt chocolate in a medium sized heat safe bowl in 30 second intervals at 50% power. Stir after each 30 seconds. Continue until chocolate is completely melted.

Add 1 cup of batter to the chocolate. Mix well.

Lightly grease a 10-inch loaf pan with baking spray. Line your pan with parchment paper (this makes removing the bread easier).

Add large spoonfuls of alternating batter throughout the loaf pan. Swirl gently with a knife, be careful not to over swirl.

Bake for 65-75 minutes or until a cake tester comes out clean.

Cool on a wire rack before removing the loaf from the pan. Store in an airtight container or freeze, wrapped and labeled well.