Set oven to broil. Adjust the oven rack close to the top burners. While allowing the oven to get fire hot, add 12-13 slices bread to a baking pan. Brush with a light coat of olive oil, then sprinkle each bread with garlic granules (optional). As the tops toast, keep a watchful eye as they burn fast. Once tops brown and crisp, flip and lightly brown the bottoms. Remove and let cool. Ovens vary but in mine, this process takes about 6-7 minutes.
Basil Arugula Pesto
In a small processor, combine walnuts, 3 of the 4 cloves garlic, salt and pepper. Pulse until fine chopped, then add the greens and oil; continue to pulse until the mixture's blended, spreadable and ingredients are even in distribution.
Red Onion Mix
In a large skillet, heat 1 tablespoon oil over medium. Once glistening, add remaining one clove minced garlic, stirring constantly for 30 seconds. Then add onions, oregano (or rosemary) and a generous pinch of salt. Stir every so often until softened and browned, about 20 minutes.
Peach Pesto Assembly
Spread a teaspoon or so pesto onto each bread, then layer with red onion mix and top with a few peach slices, shaved parmesan. Sprinkle with cracked pepper and coarse salt.