1. Preheat the oven to 225 degrees . Whisk together mayonnaise, 1/3 cup buttermilk, lemon juice, cornstarch and white or black pepper in a small saucepan; simmer, whisking, until thickened and slightly frothy, 2 to 3 minutes. Add butter and whisk 1 minute more; keep hollandaise sauce warm over a very low flame.
2. In a medium bowl, whisk together flours, cornmeal, flaxseed, baking powder, baking soda, 1/4 teaspoon salt and 1/2 teaspoon black pepper. In a separate medium bowl, whisk together remaining buttermilk, 5 eggs and oil. Add dry ingredients to egg mixture and whisk until just combined.
3. Heat a waffle iron and ladle batter into center, cooking waffles until golden and crisp on the edges. Transfer to a plate, cover with foil and place in oven to keep warm.
4. Bring 4 inches of water to a boil in a large deep saucepan. Add vinegar and reduce heat to a vigorous simmer. Crack remaining eggs into 4 small ramekins and gently slip them into pan one at a time. Cook until whites are opaque but yolks are still runny, 2 to 3 minutes. Meanwhile, place spinach and water in a large bowl and microwave until wilted, about 1 minute. Season with remaining salt and black pepper.
5. Top each waffle with an equal amount of spinach and a poached egg; drizzle with hollandaise sauce and sprinkle with paprika if desired.