- 1 Tablespoon butter, softened
- 1 loaf sourdough bread, cubed, divided
- ½ red onion, finely diced
1 pound fresh Ahi tuna, roughly chopped
- 2 cups cauliflower florets
1½ cups frozen peas, thawed
2 x 10.5-ounce cans condensed mushroom soup
- ¾ cup whole milk
- ½ cup fresh flat-leaf parsley, chopped, divided
- 1 cup shredded Parmesan
- kosher salt
- freshly ground black pepper