This chocolate marbled banana crumb coffee cake is irresistibly soft, moist, and tender, with a rich, buttery crumb and a delightful chocolatey crunch. Swirls of vanilla and chocolate batter come together to create a marbled pattern, then it’s finished with a buttery cocoa crumble, generously studded with chocolate chips, for the perfect crisp topping.

Why you will love this chocolate marbled banana crumb coffee cake

The perfect banana and chocolate combination – Every bite is packed with the delicious flavours of sweet banana and rich chocolate.

Incredibly moist – This loaf has a soft, tender crumb that stays moist and flavourful.

A delightful cocoa crumb topping – The crunchy cocoa crumb provides a delicious contrast to the soft banana cake, adding extra texture and chocolate flavour.

Perfect for breakfast, brunch, or an afternoon pick-me-up, this loaf can be enjoyed any time of day.

Simple ingredients, great results-This recipe uses everyday ingredients to create a delicious homemade loaf.

Ingredients for chocolate marbled banana crumb coffee cake

Flour– Flour provides structure and stability to the loaf. When mixed with water, its proteins develop gluten, creating a stretchy, elastic network that traps air bubbles. During baking, these bubbles expand, giving cakes a light texture.

Cocoa Powder – Gives the cake its rich chocolate flavour. My favourite is Barry Amber Cocoa Powder Extra Brute, which adds a deep, intense chocolate taste.

Granulated Sugar – White granulated sugar is used to make the cocoa crumb topping, helping to create its crisp, crumbly texture.

Light Brown Sugar – Adds sweetness and helps the loaf develop a beautiful golden-brown colour as it bakes. The molasses in the sugar enhances the flavour and adds moisture, resulting in a soft, tender crumb.

Salt– Balances the sweetness of the bread and enhances the flavour of the loaf.

Bananas– Soft, overripe bananas with brown spots are essential, adding natural sweetness and ensuring a tender, moist texture.

Eggs – The proteins in eggs help bind the ingredients together, while whisking incorporates air into the mixture, contributing to the cake’s rise and fluffy texture. Eggs also help create a smooth batter, while adding moisture and richness, ensuring the bread remains soft, tender, and flavourful.

Butter– Melted unsalted butter enhances the bread’s richness and depth of flavour. It creates a tender, moist texture by coating the flour’s proteins and limiting gluten formation. I have experimented with melted butter and oil in banana bread and found that a balanced mix of both yields the best results. The butter adds rich flavour, while the vegetable oil enhances moisture for a perfectly tender texture. If using oil use a neutral oil like vegetable or sunflower oil.

Yoghurt– adds moisture to the banana bread. Combined with baking soda, it produces carbon dioxide, helping the bread rise. If you don’t have Greek yoghurt, sour cream will also work.

Coffee – Enhances the flavour of the cocoa, making the chocolate taste richer and more pronounced.

Vanilla extract- it enhances flavour and adds depth of flavour to the loaf

Chocolate chips– I used semi-sweet chocolate chips in this recipe, but you can substitute them with milk or dark chocolate based on your preference.

How to make the loaf

First make the Cocoa Crumb Topping

In a medium bowl, combine the flour, granulated sugar, light brown sugar, cocoa powder, and salt.

Pour in the melted butter and mix with a fork until coarse crumbs form.

Stir in the chocolate chips.
Place the crumb topping in the refrigerator while you prepare the batter.

Make the Banana Batter

Preheat the oven to 160°C fan / 180°C conventional / 350°F.
Grease and line a 9 × 5-inch (23 × 13 cm) loaf tin, leaving some overhang on the sides to make removal easier.
In a medium bowl, sift together the flour, baking powder, bicarbonate of soda, and salt. Set aside.
Mash bananas and set aside.
In a large bowl, whisk together the sugar and eggs until well combined.
Add the mashed bananas, yoghurt, vanilla extract, and melted butter, and whisk until smooth.

Gently fold the dry ingredients into the wet ingredients until just combined. Be careful not to overmix.
Transfer approximately 250 ml (1 cup) of the batter to a separate bowl.
Stir the cocoa powder and coffee into the reserved batter until fully combined.

Assemble and Bake

Alternate spoonfuls of the banana batter and chocolate batter into the prepared loaf tin.
Using a knife or skewer, gently swirl the batters together to create a marbled effect. Avoid over-swirling to preserve the contrast between the banana and chocolate batters.
Sprinkle the chilled crumb topping evenly over the batter.

Bake for 50-55 minutes, or until a skewer inserted into the centre comes out clean or with a few moist crumbs attached.
Allow the loaf to cool in the tin for 15 minutes before carefully lifting it out and transferring it to a wire rack to cool completely.
Let it cool completely before slicing.

Tips for making this chocolate marbled banana crumb coffee cake

Use a kitchen scale. For consistent and accurate results, weigh your ingredients instead of measuring by volume. Incorrectly measured dry ingredients, like flour, can lead to dry, unevenly baked goods.
You can prepare the crumb mixture up to 2 days in advance and store it in the fridge.
Use room temperature ingredients. Allow yogurt and eggs to reach room temperature before baking. This helps the batter mix evenly and ensures a perfectly baked cake.
Avoid overmixing the batter. Overmixing develops gluten, which can make the bread dense and rubbery. Mix just until combined.
Preheat your oven. Ensuring the oven reaches the correct temperature before baking helps achieve even cooking and the best texture.

For more loaf breads, check these out:

Chocolate Loaf Cake
Cinnamon Streusel Coffee Loaf Cake
Snickerdoodle Banana Bread
Biscoff Banana Bread