Butter a 20 x 20cm baking tin and line with baking parchment. Heat the oven to 180C/160C fan/gas 4. Melt the butter and 150g of the white chocolate in a heatproof bowl set over a pan of simmering water, or in the microwave in 10-second bursts. Cool slightly, then beat in the sugar until smooth.

Crack in one egg and mix to combine, then add a spoonful of the flour. Repeat with the remaining eggs, then sift in the remaining flour and add the remaining chopped white chocolate. Fold to combine.

Pour a quarter of the batter into the prepared tin, then nestle the mince pies into the mixture. Pour the remaining batter into the tin around the mince pies, then bake for 35-40 mins until the top is golden brown. Leave to cool for 15 mins before removing from the tin to cool completely. Cut into 16 squares.