Clean the radicchio, remove the outer leaves, cut in half lengthways and cut out the white and bitter stalk. Rinse off briefly and place in water. Remove the bitter substances for 30 minutes, then strain and drain well.
Cut the bacon into thin strips. Cap the onion at both ends, peel and quarter lengthways. Halve the larger, outer quarters lengthways. Cap the garlic at both ends, peel and cut lengthways into strips.
In a larger pan, heat 2 tablespoons of the olive oil together with the chilli oil, add the lean bacon and fry for 1 minute. Reduce the heat a little and add the onion skins, stir-fry for about 3 minutes. Mix in the garlic cloves. Reduce the heat further and add the radicchio over a low heat. Fry for about 5 minutes, turning twice.
Season with salt, the freshly ground pepper and the balsamic vinegar, drizzle with the remaining olive oil. Garnish with almond flakes as an accompaniment to roasted or grilled meat and serve warm.