-
Begin by sifting together the flour, baking powder and salt.
-
In the bowl of an electric mixer, beat together the eggs, sugar and vanilla at high speed until very foamy.
-
Melt the butter and mix in the vegetable oil.
-
Slowly add this butter and oil mixture to the egg and sugar mixture as it continues to beat.
-
Fold in the dry ingredients alternately with the 1 cup whole milk, at room temperature.
-
When alternating wet and dry ingredients, always begin and end with the dry mixture. Here I folded in the flour in three divisions and the milk in two divisions.
-
Divide the batter in two equal portions and pour half of the batter into the greased and floured pan.
-
To the remaining half of the batter quickly beat in the cocoa and 3 tbsp milk.
-
Spoon the chocolate batter in large spoonfuls all over the surface of the vanilla batter in the pan. Using the handle of a wooden spoon, swirl the chocolate batter through the vanilla batter in a random pattern
-
Add the crumble topping by squeezing together handfuls of the crumb mixture and breaking off small pieces which get scattered all over the surface of the batter.
-
Bake for 50-60 minutes or until a toothpick inserted in the center comes out clean. The toothpick test is definitely the best way to ensure this cake is fully baked.
-
Cool in the pan for about 10 minutes before inverting onto a wire rack covered in a clean tea towel.
-
Remove the pan and then placing another wire rack on top and flipping the cake again so that the crumble is on top. Serve warm or cold. You can drizzle some chocolate ganache over the top if you like.