Combine first 5 ingredients in a small bowl and whisk until smooth.
Heat a heavy skillet over med-high heat and add oil once hot. Sauté onions, pepper, celery, carrot, and Serrano until soft (5+ minutes). Add garlic, thyme, Ancho chili powder, a large pinch of salt, and several turns of pepper. Sauté an additional 2-3 minutes until fragrant (careful not to burn the garlic). Remove from heat and set aside to cool.
In a large bowl, combine half of the sauce, beef, pork, eggs, breadcrumbs, tequila, and sautéed vegetables. Mix with hands until homogeneous. Add more breadcrumbs as needed if the mixture is too liquidy. Careful not to over kneed, as the meat will become tough if overworked. Form the mixture into a loaf on the heavy skillet (if oven proof) or a Pyrex baking pan. Coat the loaf thoroughly with the remaining sauce, and cover with an arrangement of fresh sage leaves (you don’t need a ton, just enough so that every slice will have one or two leaves).
Bake uncovered for 10 minutes at 425F then lower heat to 350F and bake for another hour or until the internal temperature is about 160°F Cover and rest for 10-15 minutes, slice, sprinkle lightly with grated Pecorino cheese, and serve.