To make your dulce de leche, add your tin of condensed milk to a saucepan filled with water. Ensure the tin is fully submerged before covering with the lid and placing over a medium heat. Bring to a boil before reducing the heat to a simmer.

Boil for 2.5 hours but make sure the tin is fully submerged at all times - top up the water when needed.

Once done, allow the tin to sit in the water to cool. Once the water has cooled, drain and allow the tin to come to room temperature. When cool enough to touch, transfer contents to a bowl, mix well until smooth, cover and leave to one side.

For the loaf, preheat oven to 150C Fan /340Fand grease and overline 1x2 lb deep loaf tin. Please note you want a tin with deep sides for this cake. If you have a regular 2.5 inch deep tin, use ¾ of the batter and bake the rest as cupcakes/muffins OR opt for an 8 inch round tin.

Lower the oven rack to no higher than the middle to ensure the loaf doesn't brown too quickly when baking.

Using either a stand mixer with a paddle attachment fitted or an electric hand held whisk, cream together the butter, oil and sugar on a medium to high speed for at least 5 minutes.

Add the eggs, mixing well between each addition (give these a minute or two at a time).

Next you want to go in with the vanilla bean, soured cream, and bananas. Mix again to combine.

In a bowl, add the flour, cinnamon, ground cardamom, baking powder, bicarb and salt and give it all a good mix to combine.

Add the flour mix and chopped chocolate to the bowl in three parts, running the mixer on a low speed to gently incorporate.

Once there are a few flour streaks remaining, transfer half of the batter to another bowl and sprinkle in the cocoa powder and buttermilk. Use a rubber palette knife to fold through until well combined.

Add 250g dulce de leche to a piping bag.

Use 2 ice cream scoops or spoons to add spoonfuls of batter to the tin, alternating each time between the chocolate batter and the vanilla (this will help to give a marbled effect when sliced). Every so often, pipe the dulce de leche onto the batter - interspersing all that delicious goodness throughout the whole loaf. Be generous with it, we want pools of the dulce de leche running through each slice.

Once all the batter has been added, give the tin a little shake to help spread the batter and use up any remaining dulce de leche on top before sprinkling over the demerara sugar on top to cover.

Pop in the oven and bake for 65 to 70 mins. Halfway through, rotate the tin and place some foil on top to cover to prevent further browning.

Depending on your oven, you may need a touch more time but check if the bread is done by inserting a toothpick to ensure no batter returns.

Remove the tin from the oven and allow the loaf to sit in the pan for 15 minutes, before covering the top with some clingfilm/ saran wrap.

Allow it to cool completely before turning out onto a cooling rack. Once cooled, make the choc glaze by adding all the ingredients to a pan and place over a low to medium heat. Gently melt the chocolate and combine the ingredients until the sauce has lightly thickened

Let the glaze to cool slightly before placing a baking tray under your cooling rack.

Pour the glaze over the baked bread and use a palette knife to remove any surplus from the tops and sides. Once covered, leave to set.

Use a serrated knife to slice