To make Olive Garden Alfredo Sauce, heat 1 1/2 cups of milk and 1 1/2 cups of heavy cream over medium-low heat in a saucepan. Once the mixture begins to simmer, turn the heat off, and slowly whisk in 1/2 cup each of grated Parmesan and Romano cheeses.
When the cheese has been mixed in and is starting to melt, remove the pan from the burner. Separate the yolks from six jumbo eggs into a large bowl. Pour a bit of the warm milk and cream mixture into the bowl with the eggs and whisk together, then add the eggs into the saucepan with the rest of the milk and cheese.
Place the sauce back on very low heat and stir continuously until it reaches a simmer again, then take it off the heat. The sauce thickens as it cools. Season the Alfredo sauce with salt and pepper to taste, and serve it over pasta. It can also be used as a warm dip for bread or crackers.
This recipe is from the official Olive Garden website. Popular imitation Olive Garden Alfredo sauce recipes may differ. For instance, some recipes for Alfredo sauce call for butter, minced garlic or other seasonings.