For the sauce, blend the egg yolks, sugar, mustard, seasoning, white wine vinegar and lemon juice in a food processor. Gradually add the oil while the motor is running to make a thick and creamy mayonnaise.
Fold in the spinach and set aside in the fridge. For the waffles, mix the gluten free flour and baking powder together in a bowl.
Mix the mashed potato, lactose free milk and butter together in a separate bowl, then fold in the flour mixture.
Whisk the egg whites in a bowl until stiff peaks form when the whisk is removed. Fold the egg whites into the mashed potato mixture.
Lightly oil and heat a waffle iron. Pour some of the mixture into the waffle iron and cook for 3-4 minutes, or until golden-brown and cooked through. Set aside to a plate and keep warm. Repeat with the remaining mixture to make five more waffles.
To serve, heat a pan of water until boiling. Crack the eggs carefully into the water and poach until the whites are firm but the yolks are still runny.
Remove the eggs from the pan using a slotted spoon and drain on a plate lined with kitchen paper. Place a waffle onto each serving plate, top with a poached egg and spoon over some sauce.