Cut and peel the pattypan squash and potatoes into small cubes. Slice the onion.

Place the vegetables, potatoes, onion, water, and salt in a skillet.

Cook over medium heat for 15 minutes, stirring regularly.

Preheat the oven to 400°F (200°C).

Transfer the ingredients from the skillet to a mixing bowl. Add the diced ham, nutritional yeast, soy cream, and pepper. Mix well.

Pour the mixture into a baking dish, sprinkle with shredded Swiss cheese, and bake for 30 minutes at 350°F (180°C).