Pre-heat your oven to 160C Fan/350F/Gas Mark 4 and grease and line a 9" square traybake tin (you can bake them in other tin sizes, see above for details)
Melt the dark chocolate and butter together in a pan on a low heat, stirring as they melt. When fully melted, remove from the heat. Let it cool for 5 minutes
In a mixing bowl, whisk together the dark brown soft sugar and the eggs for exactly 5 minutes using an electric mixer, set a timer for accuracy
Slowly pour the melted chocolate and butter into the egg and sugar mixture, whilst constantly whisking on a slow speed
Add the plain flour and mix in gently
Fold in the chopped cherries and chocolate chips, and pour the batter into the lined tin
Mix the kirsch into the cherry jam and add spoonfuls of it over the brownie batter. Use a butter knife to gently swirl it around
Bake for 30-35 minutes, or until a toothpick inserted comes out with several moist crumbs on, but is not wet
Leave it to cool completely, then chill in the fridge for at least 2 hours before cutting into squares. Ideally serve with whipped cream
Store in an airtight container in a cool place and eat within 3-4 days