Peel peaches, cut in half, remove and discard the pit, and chop into small pieces.
In a large, non-reactive pot, combine the peaches, onion, raisins, vinegar, honey, pepper, salt, chili flakes, lemon zest and juice. Bring the mixture to a simmer and cook, stirring occasionally, for about 20 minutes or until most of the vinegar has cooked off and the mixture thickens. Remove from heat and place pot into pre-prepared ice bath. Chutney can be kept covered in the fridge for a week.
When you’re ready to make your sandwiches, heat up your griddle or pan to medium heat. Cut the sourdough into one inch slices (you’ll need 8 slices here) and generously butter the outsides.
Mix the cheeses together in a mixing bowl with the basil. Divide the cheese between four of the slices.
Place a few tablespoons of peach chutney on top of the cheese mixture and close up each sandwich.
Griddle each sandwich for 3 minutes per side or until lightly browned. If you have a heavy lid for some weight on top, that will help the filling stay together.