In a large bowl, sift together flour, brown sugar, baking powder, baking soda, salt, and 1 tablespoon pumpkin pie spice. Stir to incorporate.
In a medium bowl, whisk canned pumpkin, 11/2 cups milk, butter, egg yolks, and vinegar. Fold wet ingredients into the dry ingredients.
In a small bowl, beat egg whites until soft peaks form. Fold whites into batter, careful to stir as little as possible.
Grease and heat skillet over medium heat (300 F in an electric skillet). Pour 1/3 cup batter into skillet. Cook pancakes about 3 minutes per side. Try flipping the first pancake a few times to get a sense of the best cook time. Cook remaining pancakes.
To make syrup, whisk together sweetened condensed milk, vanilla, 1 teaspoon pumpkin pie spice, and 1 tablespoon milk in a small bowl. Serve immediately.
Per serving: 386 calories, 10 grams fat (5.5 grams saturated fat), 81 milligrams cholesterol, 530 milligrams sodium, 64 grams total carbohydrates, 2.5 grams fiber, 11 grams protein.