Begin by slicing the yellow onions into ⅛-inch rings, ensuring even thickness for uniform cooking. Remove any brown or blemished areas.

In a large pot, heat 2 tablespoons of olive oil and 2 tablespoons of butter over medium heat. Add the sliced onions along with a pinch of salt and pepper. Stir occasionally for about 30-35 minutes until golden brown.

Add 4 minced garlic cloves, red pepper flakes, Worcestershire sauce, and soy sauce to the pot. Sauté for 30 seconds until fragrant.

Pour 4 cups of water into the pot and half of the can of evaporated milk, stirring to combine. Whisk 1 tablespoon of cornstarch with the remaining evaporated milk until smooth and add that to the pot. Increase heat to high and bring to a boil.

Once boiling, add 12 ounces of orecchiette pasta and reduce to a simmer. Cook uncovered for 20-25 minutes, stirring often until pasta is al dente.

Remove from heat, stir in 1 cup of grated Gruyere cheese until melted, then add ½ cup of grated Parmesan cheese, mixing until smooth.