Caramelized Onion Waffles: Heat 2 tablespoons oil in large skillet over low heat. Add onions and cook until caramelized, about 20 minutes. Stir frequently. Remove onions from skillet and rough chop; cool. Onions can be prepared ahead and refrigerated.
Combine onions with eggs, milk and 3 tablespoons oil in a large bowl. Whisk until smooth.
Mix flour, baking powder, salt and spices in a large bowl. Add wet ingredients to the dry and mix until combined.
Pour waffle batter into preheated waffle iron and cook according to manufacturer's directions or about 4 to 6 minutes. Repeat with remaining waffle batter. Sandwiches are best made to order.
Sandwich: Heat sausage patties until hot and well browned. Place on sheet tray and top with a mound of cheese. Warm to melt the cheese in a 300ºF oven.
Cut waffle in half or if a Belgian waffle, split horizontally. Top bottom waffle with a sausage and cheese, fried egg, arugula and waffle top.