In a large nonstick skillet, heat 2 tablespoons olive oil over medium-high heat. Add shallots, 1⁄4 cup balsamic vinegar, 1⁄2 teaspoon salt, and 1⁄4 teaspoon pepper. Cook for 5 to 6 minutes, stirring occasionally. Remove from skillet, and set aside.

In skillet, heat remaining 3 tablespoons olive oil over medium-high heat. Add green beans; cook for 10 minutes, stirring frequently. Add remaining 1⁄4 cup balsamic vinegar, remaining 1⁄2 teaspoon salt, remaining 1⁄4 teaspoon pepper, butter, brown sugar, and garlic, stirring until butter is melted. Add reserved shallot; cook for 1 minute until heated through. Garnish with almonds, if desired.