Smash 4 garlic cloves and combine with olive oil in a small bowl. Set aside and allow to sit for 30 minutes. Trim the radicchio heads, cut into wedges, set aside.
In a small saute pan, melt the butter over low heat and add the red pepper flakes, panko, minced garlic, and salt. Stir until panko gets crispy and golden brown. Remove from heat. Cool the mixture for a few minutes and stir in parsley.
In a small saucepan, over medium-high heat, gently simmer until the balsamic vinegar is reduced by half.
Preheat grill or grill pan to high. Brush radicchio with infused olive oil, season with salt and pepper. Place cut sides down on grill and cook for 1 to 2 minutes, turn to other cut side, grill for 1 minute, turn to back, and grill for 1 minute more.
Remove wedges to a serving platter. Sprinkle the bread crumbs over the radicchio wedges, drizzle with the reduced balsamic, and serve immediately.