Use 2-3 day-old bread for the best panzanella salad.
Add the crushed garlic, salt, pepper, rosemary, balsamic vinegar, mustard, honey, and first quantity of olive oil to a mason jar (or another vessel that has a tight-fitting cap). Screw the jar's cap on tightly and shake vigorously to emulsify the dressing.
Set aside. *This dressing may be prepared a week in advance.
Preheat your oven to 450°F.
Use a chef's knife to slice off the bottom of the mushroom's woody stem. Discard the sliced ends.
Cut the larger mushrooms- anything bigger than a golfball- into quarters. Cut the smaller mushrooms- golfball-size- in half. Anything smaller than a silver dollar- leave whole.
Pour a 1/4 cup of the balsamic vinaigrette over the mushrooms. Toss the mushrooms in the dressing to coat them completely, then arrange the mushrooms with one cut side touching the pan to ensure they caramelize completely.
Roast the mushrooms for 15-20 minutes, or until they are a deep brown color and have developed a crust.
Remove the pan from the oven and allow the mushrooms to cool while you prepare the rest of the salad.
Decrease the oven's temperature to 300°F.
Pour the remaining 1/4 cup of extra virgin olive oil onto a sheet pan. Toss the bread cubes into the oil to coat them lightly.
Toast the bread in the oven for 10 minutes.
Remove the pan from the oven, toss the bread cubes again, then return the pan to the oven to toast for an additional 10 minutes.
Pull the pan out of the oven and let the bread cool down while you assemble the salad.
Pour half of the vinaigrette into the bottom of a large salad bowl.
Add the toasted bread cubes to the bowl, followed by the roasted mushrooms, arugula, tomatoes, red onion, and the chopped parsley.
Pour the remaining dressing over the contents of the bowl and toss the salad together until the vegetables are coated and the bread is flecked with vinaigrette.
Transfer the salad to either a serving platter, or to individual plates.
Top the salad with the crumbled chèvre and serve immediately, or allow the salad to rest for 30 minutes*.
Panzanella tastes best the day it is prepared, but can be stored- in the refrigerator- for up to 24 hours.
If you're using fresh bread: toss the bread cubes a third time and toast for another 10 minutes- for a total of 30 minutes. This additional 10 minutes of toasting is only for freshly-baked bread.
*Allowing the dressed panzanella to sit for a half-hour gives the bread a chance to soak up, not only the dressing, but the tomato juice as well.