Cook potatoes in boiling, salted water for 5 to 8 minutes, or until soft.

Drain the potatoes and set them aside.

Heat olive oil in a medium saucepan over medium-low heat.

Add onions and cook for 15 to 20 minutes, or until soft and translucent.

Add garlic and cook for 1 to 2 minutes more.

Dissolve cornstarch in 1/2 cup cold water in a small cup.

Add the cornstarch mixture to the onion mixture, increase heat to medium, and simmer for 5 minutes, stirring occasionally.

Add nutritional yeast and salt, and simmer for 5 minutes more, stirring occasionally.

Remove from heat and add potatoes and 1/2 cup white wine.

Blend with an immersion blender until smooth and silky.

Return to heat and simmer gently for 5 minutes.

Add remaining 1/2 cup wine, and cook for 1 minute, stirring once or twice, or until the fondue is thickened.

Transfer to a fondue pot, sprinkle with nutmeg, and serve with dippers (bread, apples, etc.).