Instructions

Step 1
Preheat oven to 170C/150C fan-forced. Using extra butter, grease the base and side of a 2-litre (8-cup-capacity) ovenproof glass bowl (see Notes). Cut two 5cm x 30cm strips from baking paper. Line base and side of bowl with the paper strips so they form a cross, then fill in the gaps with extra baking paper, cutting to fit.
Step 2
Using an electric mixer, beat butter, sugar and vanilla until light and fluffy. Add eggs, 1 at a time, beating well after each addition. Sift flour over butter mixture. Add milk. Stir until well combined. Divide mixture evenly among 3 bowls. Tint 1 batch bright blue with blue food colouring. Tint second batch pale blue with blue food colouring. Leave third batch plain. Place alternate spoonfuls of the 3 batches into prepared bowl. Using a skewer, swirl together to create a marble effect. Bake for 1 hour 15 minutes or until a skewer inserted into the centre comes out clean. Cool cake in bowl for 10 minutes. Turn out onto a wire rack to cool completely.
Step 3
Meanwhile, make Frosting Using an electric mixer, beat butter in a small bowl until light and fluffy. Gradually add icing sugar until well combined. Tint frosting grey with black food colouring.
Step 4
Place cake on a cake stand or board. Spread frosting all over cake. Push white chocolate melts and choc bits, flat-side up, into the frosting to form craters. Top with astronauts. Serve.