Creamy Winter Squash Soup with Herbed Crostini

medium peeled and cut into 2-inch cubes 1 pound yukon gold potatoes

Garlic cloves, minced (2 teaspoons), small

Onion, finely chopped (1 cup), medium

Rosemary, stems fresh

Sage, fresh leaves

Chicken stock, homemade or store-bought low-sodium

Salt and freshly ground pepper, Coarse

Herbed crostini

Butter, unsalted

Water

2 pounds buttercup, butternut, Hubbard, or kabocha squash, peeled, seeded, and cut into 2-inch cubes