Begin by melting 1 tablespoon of unsalted butter in a heavy-bottomed pan over low to medium heat. Add the finely diced onion and sauté for 30 to 40 minutes, stirring occasionally, until the onions are soft, deeply caramelized, and golden brown.

Once the onions are beautifully browned, add minced garlic to the pan. Sauté for an additional 1 to 2 minutes, stirring constantly until the garlic becomes fragrant but not burnt.

Add the remaining tablespoon of butter to the mixture and let it melt completely. Gradually whisk in all-purpose flour, stirring continuously for about 10 to 15 minutes until the roux transforms into a rich amber color.

Slowly stir in the apple cider and Worcestershire sauce, blending until the mixture is smooth. Allow it to cook for another 3 to 5 minutes.

Gradually add chicken stock to the pan while stirring to prevent lumps from forming. Mix in salt and fresh ground black pepper to season. Bring the mixture to a gentle simmer.

Add the fresh sage leaves to the simmering gravy, stirring gently to combine. Let the mixture simmer for about 10 minutes, or until it slightly thickens.

Taste your Cider and Sage Gravy and adjust the seasoning as needed. If desired, remove the sage leaves or use an immersion blender for a smooth texture.