In a small pot over low-medium heat, add blackberries, sugar and lemon juice. With a potato masher gently burst all the berries until a thin sauce forms.
Turn up heat to medium-high and allow the sauce to bubble and reduce until thickened, stirring frequently. The sauce will thicken, just keep bubbling and stirring. Keep in mind it will continue thickening once it cools.
Butter one side of each of your slices of bread. In a large pan with the heat OFF add two slices of bread butter-side-down (or as many as you can fit). Spread 1 heaped tbsp blackberry jam, top with 3 wedges of brie each, 2 slices of bacon then a pinch of chilli flakes (optional). Add another slice of bread on top then spread with butter.
Turn heat to a medium and fry both sides until golden, with the brie starting to leak out. Repeat with remaining sandwiches if needed then slice in half and enjoy!
