Set a large nonstick or well-seasoned skillet over medium heat. Add 1 teaspoon of the butter and 2 teaspoons of the oil. When the butter melts, add the Spam slices in a single layer. Cook until deeply golden on both sides, turning once. Transfer the Spam to a plate and keep it warm.

Add the remaining oil to the skillet. Add the mushrooms and a pinch of black pepper. Cook, stirring occasionally, until they are browned and their moisture has cooked away.

Push the mushrooms toward one side of the skillet. Place the tomato halves cut-side down in the open space and cook until lightly browned and softened. Turn them over and season lightly with pepper.

Warm the baked beans in a small saucepan over medium-low heat, stirring often, until hot. Alternatively, spoon them into a microwave-safe bowl, cover loosely, and microwave until hot, stirring once. Keep warm.

Toast the bread. Spread the hot toast with the remaining butter.

For the eggs, make four open spaces in the skillet and add a small amount of oil or butter if the pan looks dry. Crack one egg into each space. Cook until the whites are set and the yolks are cooked to your preference. Cover the skillet briefly if you prefer a film over the yolks.

Divide the Spam, mushrooms, tomatoes, baked beans, eggs, and buttered toast among four plates. Sprinkle with parsley, if using, and serve immediately.