Don't be put off by the combination of chocolate and banana. Milk chocolate is soft and subtle, and it gives the coffee cake its signature sweet "swirl" without overpowering. The banana gets a tropical boost from the coconut oil and vanilla, and the result is a luscious little cake. The streusel topping takes it to a level that might make you forget banana bread forever.
Note: I use a lot of "good vanilla" in my recipes, which to me usually means Mexican or Tahitian vanilla. I get mine once a year in Mexico, but you can also find good variations, like San Luis Rey, in upmarket grocery stores like Central Market or Whole Foods. —TRISH MURPHY
Preheat the oven to 350F. Spray a Bundt pan with cooking spray, or use a loaf pan or 8"x8" glass pan.
Combine the streusel ingredients in a small bowl and mix with a fork until crumbly and slightly moist. Add another pat of butter if needed to make it uniform in texture.
Whisk the coconut oil and sugar together in a large mixing bowl until light and fluffy. Add the eggs one at a time, beating well after each addition. Add the yogurt and vanilla and mix well.
Combine the flour, baking powder, baking soda, salt and nutmeg in a mixing bowl. Fold the flour into the egg mixture in thirds, alternating with the addition of the banana puree. When all the flour is incorporated, fold in the chocolate chips. Pour the batter into the prepared pan and sprinkle the streusel evenly over the top to completely cover it. Pat it down lightly with a spatula. Bake for 30 minutes, then cover the cake loosely with foil and continue baking another 25-30 minutes or until a knife inserted in the center comes out mostly clean. Cool the cake in the pan. Slice and serve while still slightly warm.