Preheat your oven to 425°F. Make sure to grease an 8x8 inch baking dish, with butter.
In a pot melt the two tablespoons of butter over medium heat. Add the chopped onion and cook until it turns soft and translucent which usually takes 5 minutes. Stir in the minced garlic and season with salt and pepper cooking for 30 seconds.
Incorporate the chicken stock, heavy cream and sliced potatoes into the pot. Bring the mixture to a simmer without letting it reach a boiling point. Cover the pot. Lower the heat to low. Allow it to cook until the potatoes become tender around 15 to 20 minutes. Adjust seasoning as required.
Carefully transfer the potato mixture into the baking dish ensuring an even distribution throughout. Sprinkle grated cheddar, provolone and Parmesan cheese on top.
Place in the oven and bake until bubbly while achieving melted cheese; this usually takes about 10 to 15 minutes.
Once done serve your version of Ruth's Chris Potatoes Au Gratin garnished with chopped parsley for a burst of color and freshness.
