Melt butter in a Dutch oven over medium heat; add onion, peppers, and garlic; sauté 10 minutes or until tender.
Add mushrooms, and cook 30 minutes or until liquid evaporates. Stir in bread cubes, lightly beaten eggs, and breadcrumbs. Gradually stir in chicken broth until the mixture resembles stuffing. Stir in herbs, green onions, salt, and pepper. Cover and chill 8 hours.
Shape mixture into 16 patties, using about 3/4 cup mixture for each patty. Cook, in batches, on a nonstick griddle or a large nonstick skillet coated with cooking spray over medium-high heat 4 minutes on each side or until golden. Place cakes on a wire rack in a jellyroll pan, and keep warm in a 200° oven.
Cook spinach and 1 tablespoon water in a large nonstick skillet over medium heat 5 minutes or until wilted, stirring once; drain well. Place 1/4 cup spinach on each of 8 serving plates; top with two mushroom cakes. Top with 2 poached eggs and Tasso Hollandaise. Serve with asparagus, if desired. Garnish, if desired.