Nutella Brownies

Bahan-bahan (12 porsi)

• 1/3 cup (5 Tablespoons; 71g) unsalted butter, softened to room temperature
• 1/2 cup (100g) packed light brown sugar
• 2 large eggs, at room temperature
• 2 teaspoons pure vanilla extract
• 1 and 1/4 cups (370g) Nutella, divided
• 1/2 teaspoon salt
• 3/4 cup (94g) all-purpose flour (spooned & leveled)
• optional: 3/4 cup (135g) semi-sweet chocolate chips; a sprinkle of sea salt