2 slices bacon, cut into 1-inch pieces
1/3 cup chopped onion
2 tablespoons butter
1 cup (1/2-inch) butternut squash, peeled, seeded and cubed
1/2 cup frozen corn kernels, thawed
2 tablespoons chopped fresh basil leaves, plus more for garnish
1 1/2 teaspoons dry mustard
1/2 teaspoon salt
1/2 teaspoon ground black pepper