Begin by preheating your oven to 325°F (165/145C Fan) and lining a square baking dish with parchment paper.
In a large mixing bowl, whisk together the wet ingredients - the eggs, oil and cherry syrup (or liqueur).
In a separate mixing bowl, sift together the flour, powdered sugar, superfine granulated sugar and cocoa powder.
Add the sugar mixture to the wet ingredients and stir using a spatula until it has just combined into a thick brownie batter.
Reserve about a third of the cherry halves and a third of the chocolate chips. Add the rest of these to the batter and fold through.
Pour the batter into the prepared pan and carefully spread into an even layer.
Place the reserved cherries on top of the batter and sprinkle the remaining chocolate chips.
Bake in the preheated oven for about 25 minutes, until a toothpick comes out mostly clean.
Remove from the oven and allow to cool completely (at least 2 hours) before slicing.