Pre heat oven to 180°C and line a 25cm x 30cm (with at least 4cm high sides) baking tray with baking paper. Place the butter and sugars into the bowl of an electric mixer and beat on medium speed until pale in colour. Scrape down the sides of the bowl with a spatula before adding the eggs and continuing to mix on medium for a further 3 minutes

Scrape down the sides of the bowl with a spatula, then while the mixer is on low slowly stream in the oil. Increase the speed of the mixer to high and beat until the batter has almost doubled in size, about 5 minutes

Add the remaining ingredients except for the carrots and mix on a low speed until just incorporated, about 1 minute. Using a spatula fold in the carrots. Transfer the batter into the prepared cake pan

Bake for 25 minutes or until just golden and the centre springs back when touched. Let sit for 5 minutes before transferring to a cooling rack to cool completely

Cut rounds of cake using a 6cm round cutter, and using a spatula spread frosting on each round before sandwiching 2 together to form your mini layer cakes. Decorate with mini carrot decorations, available at most good cake supply shops or a walnut

Add the cream cheese and butter to the bowl of an electric mixer and beat until combined. Lower the speed of the mixer to low and gradually add the icing sugar. Increase the mixer to medium high and beat for a further 2 minutes until light and fluffy. If your buttercream is too thick add a splash of milk