Strawberry champagne cake

Strawberry and champagne jam

• 1 lemon zest only, no white pith
• 20 g freshly squeezed lemon juice
• 270 g strawberries (over-ripe strawberries are preferred)
• 100 g white sugar
• 100 g champagne

Roasted strawberries

• 500 g strawberries hulled and cut into halves
• 75 g champagne
• 10 g caster sugar

Sponge

• butter to grease
• ½ tsp bicarbonate of soda
• 1 tsp cream of tartar
• 80 g cornflour
• 30 g plain flour
• 130 g caster sugar
• 4 eggs separated, room temperature
• 1 tsp natural vanilla extract
• 2 tbsp hot water
• 300 g pouring (whipping) cream (see Tips)