Put the dark chocolate and butter in a large microwave safe bowl. Microwave in 30 second bursts, stirring between each burst, until melted. Avoid overcooking as this can negatively affect the chocolate.
Add the caster sugar. Stir through with a manual whisk - I say stir as you don’t want to add air but a whisk is still the best tool as it distributes everything quickly.
Add the eggs and vanilla. Stir with the whisk again.
Put the flour through a sieve into the bowl. Stir to combine.
Assemble the mince pie brownies
Pour about one quarter of the brownie batter into your prepared tin - just enough to fully cover the base.
Arrange the mince pies on top of the batter in a 3 x 4 pattern.
Pour the remaining brownie batter on top and level off. Tap the tin on the table a few time to ensure there are no air bubbles trapped between the pies.
Bake and serve your mince pie brownies
Bake for approximately 40 minutes until shiny on top and no wobble present when you shake the tin.
Allow to cool in the tin, then chill overnight to make them easy to slice.
Slide onto a serving board and slice in 12 rectangular pieces (in a pattern of 2 by 6).