Vegan Banana Muffins

Name: Vegan Banana Muffins
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Cuisine: American
Ingredients: 3 x (~360g total) very ripe medium bananas ((about 1 2/3 cups of mashed banana, note 1)); 1 cup (200g) packed brown sugar; 1/2 cup (120g) dairy-free milk (room temperature); 1/2 cup (110g) neutral flavored oil; 1 tablespoon white or apple cider vinegar (or lemon juice (optional)); 1 teaspoon vanilla extract; 3 cups (375g) all-purpose plain flour (spooned and leveled (note 3, and for gluten-free option)); 1/2 cup (60g) chopped walnuts (or pecans, optional); 3 teaspoons ground cinnamon; 3 teaspoons baking powder; 1/2 teaspoon baking soda; Pinch of salt; 1/2 cup (65g) all-purpose plain flour; 3 tablespoons (40g) packed brown sugar (coconut sugar, regular sugar, or granulated sweetener of choice); 2 tablespoons (30g) vegan butter (or coconut oil, melted and cooled); 1/2 teaspoon ground cinnamon