Sauté Aromatics: Heat the chicken fat or butter in a large skillet over medium heat. Add the chopped onions and cook until translucent, about 3-5 minutes. Then, add the minced garlic, thyme, rosemary, sage, and bay leaf. Cook for another minute, until fragrant.

Make the Roux: Sprinkle the flour over the onions and garlic, and stir well to combine. Cook over low to medium heat, stirring constantly, until the mixture turns a light golden color and smells nutty, about 3-5 minutes.

Deglaze the Pan: Slowly whisk in the chicken stock, a little at a time, ensuring there are no lumps, and scraping up all the flavorful bits from the bottom of the pan.

Simmer the Gravy: Bring the gravy to a simmer, then reduce the heat to low and cook for about 10-15 minutes, stirring occasionally, until the gravy has thickened slightly.

Add the Umami: Stir in the soy sauce or Worcestershire sauce, and tomato paste. Continue to simmer until the gravy reaches your desired consistency.

Finish with Cream and Acid: Stir in the heavy cream and lemon juice or vinegar, and heat through, being careful not to boil the sauce. Remove the bay leaf before serving.

Taste and Adjust: Add salt and pepper to taste. Adjust any of the other flavors as necessary.

Serve: Serve the gravy hot over mashed potatoes, roasted chicken, or your favorite poultry dishes.