Heat oven to 190C/170C fan/gas 5.
Grease and line the bottom of a round
21cm loose-bottomed cake tin. With a
wooden spoon or electric mixer, beat the
butter and sugar together until smooth
and a pale, creamy colour. In a separate
bowl, sift together the flour, baking
powder and cinnamon. One at a time,
beat each egg into the butter mixture
along with a tbsp of the dry mixture, then
beat in the milk and fold in the rest of the
dry ingredients until well combined.
In the bowl that contained the flour,
mash the bananas until smooth and
lump-free – whizz with the electric mixer
if needed – then fold into the rest of the
mixture until well combined. Spoon into
the tin and smooth over the surface. Bake
for 45-50 mins, until a skewer inserted
into the centre comes out clean. Leave to
cool for 5 mins, then remove from tin and
continue cooling on a wire rack.
Use a serrated knife to cut the cake
horizontally into 3 equal layers. Whip the
cream until it forms stiff peaks, then chop
the banana into small pieces and fold into
the cream, along with the marshmallows.
On the first layer, spread a generous
covering of the dulche de leche, followed
by half of the cream mixture. Sandwich
the second layer on top and repeat.
Thickly spread dulche de leche over the
top of the cake, then arrange extra
marshmallows around the edge.