Slice Polenta into twelve 1/2 inch slices. Fill a wide saucepan with 2 inches of water and add vinegar. Bring water and vinegar to a simmer on medium/high heat.
Heat half of the oil in a non stick frying pan over medium/high heat. Add polenta in batches and cook until crispy on the outside and soft in the middle, approximately 2-3 minutes a side. Place on a plate and keep warm in the oven.
Reduce heat to medium and add the remaining oil to the frying pan. Saute mushrooms until tender, about 2 minutes. Add the spinach and 1 tablespoon of water, stir until wilted and add salt and pepper to taste. Keep warm in pan.
Crack an egg in a small dish and slip it into the simmering water. Repeat with the remaining eggs. Poach eggs about three minutes or until the white is set. With a slotted spoon, remove eggs from water and set on a paper towel to drain.
Place two or three polenta rounds on a plate and layer one slice of cheese, the spinach/mushroom mixture and top with one or two eggs. Sprinkle with salt and pepper and top with a little grated cheese.
A crisp golden crust gives way to a soft center beneath a crown of runny yolk and earthy mushrooms. Coordinating multiple cooking elements requires careful staging.
The Sequencing Challenge
Success depends entirely on thermal management. Tube polenta contains high moisture. Slicing it into half-inch rounds and searing it in olive oil for two to three minutes per side develops the required exterior crunch. Holding these rounds in a 300 degrees F oven keeps them warm without drying them out. Mushrooms demand high heat initially to release their water content. Once the shiitakes soften, dropping the heat to medium prevents scorching before the baby spinach enters the pan with a single tablespoon of water. That brief steam collapses the greens instantly.
Water Dynamics and Egg Science
Poaching demands precision. Adding white vinegar to the simmering water lowers the pH. Acid accelerates protein coagulation, tightening the egg whites around the yolk before dispersion occurs. Crack each egg into a small vessel first. Sliding the raw egg gently from the ramekin into the liquid prevents yolk breakage. Three minutes submerged in gentle heat yields a set white and a fluid center. Removing the poached eggs to paper towels absorbs excess water, protecting the crisp polenta base from sogginess during final assembly. Fresh corn polenta requires extended simmering and cooling compared to convenient pre-cooked tubes, changing the preparation timeline entirely while yielding a denser final texture.