Lime,passionfruit & lemon grass frozen yoghurt cake

Ingredients

• 3/4 cup (110g) plain (all-purpose) flour
• 1/4 cup (35g) self-raising flour
• 1/2 teaspoon bicarbonate of soda (baking soda)
• 2 teaspoons lime rind, finely grated
• 1/3 cup (90g) firmly packed grated palm sugar
• 60 grams butter
• 1/3 cup (115g) golden syrup or treacle
• 1 egg
• 1/2 cup (125ml) buttermilk
• 1 1/2 cup (420g) greek-style yoghurt
• 300 millilitres thickened (heavy) cream
• 2/3 cup (160ml) passionfruit pulp
• 1 1/2 cup (305g) firmly packed grated palm sugar
• 1/2 cup (125ml) water
• 2 tablespoons lime juice
• 1 stalk fresh lemon grass, quartered, bruised
• 4 limes, sliced thinly