For the sausage: cook in a 400°F oven to an internal temperature of 160°F using a thermometer.
In a saucepan over medium heat, melt the butter. Add the flour and cook until it starts to turn golden brown. Stir in the milk and bring the mixture to a simmer. Stir occasionally, until the mixture thickens slightly, about 3-5 minutes. Add the spinach and cook until the spinach has wilted (about 1-2 minutes). Remove the pan from the heat and stir in the parmesan cheese. Season with salt and pepper, to taste. Cover with a lid on to keep warm. (If the sauce is too thick, thin it out with a little more milk).
Fill a saucepan halfway with water. Bring the water to a simmer. Stir the vinegar into the water. Crack the eggs into a bowl. Gently place the eggs into the water. (You can poach multiple eggs at once, being careful not to overcrowd the pan.) Cook the eggs in the water for 3-5 minutes, gently flipping over about halfway through until the whites are firm. Remove the eggs with a slotted spoon onto a paper towel to drain excess water. Season with salt and pepper.
Toast the bread.
Spoon the spinach sauce over the eggs and toast. Serve with sausage and pineapple.