Mushroom Crostini

Name: Mushroom Crostini
Ingredients: 1 (8-inch) baguette , cut into 12 1/2-inch slices; 3 tablespoons extra virgin olive oil , plus more for brushing; 1 tablespoon unsalted butter; 1/2 teaspoon brown sugar; 1/2 teaspoon kosher salt , divided; 2 medium (3 cups) yellow onions , sliced 1/4-inch thick; 8 ounces cremini or baby bella mushrooms , sliced 1/4-inch thick; 2 teaspoons minced garlic; 1 teaspoon balsamic vinegar; 1 teaspoon soy sauce; 1/4 teaspoon black pepper , plus more for garnish; 4 ounces goat cheese; 1 tablespoon sliced chives , plus more for garnish; 1/2 teaspoon garlic powder; 1/2 teaspoon onion powder