Heat the oven to 400°F (200°C). Briefly dip stiff banana leaves in hot water until pliable, then drain and pat dry. Line the 9 × 13-inch pan with overlapping leaves, leaving enough overhang to fold over the top. Reserve a piece for the lid.

Heat 10 g lard in a saucepan over medium heat. Soften onion for 5 minutes, then stir in garlic for 30 seconds. Add tomatoes and cook 5 minutes. Dissolve 20 g achiote paste in 250 ml broth and add it. Whisk 30 g masa harina with the remaining 100 ml broth; stir into the sauce and simmer 4–5 minutes until thick enough to coat a spoon without watery pooling. Fold in cooked chicken, cooked pork and optional epazote; season with up to ½ teaspoon salt. Remove from heat.

Dissolve the remaining 20 g achiote paste in 650 ml warm broth. Stir into 500 g masa harina and leave for 10 minutes. Beat the softened 140 g lard until smooth, then work into the hydrated masa with up to ½ teaspoon salt. Knead until soft, cohesive and easily spreadable, adding extra broth a tablespoon at a time only if it cracks badly. It must hold its shape, not pour.

Press about two-thirds of the masa across the lined pan base and up its sides in an even layer. Spoon in the thick filling. Flatten the remaining masa between two pieces of food wrap or parchment, remove the upper sheet, then invert the masa over the filling. Remove the other sheet and pinch the edges closed. Patch any holes with masa.

Lay a banana-leaf piece over the top and fold the overhanging leaves inward. Cover the pan tightly with foil. Bake for 90 minutes. Check that the masa is firm rather than wet and the center reaches at least 165°F (74°C); if needed, re-cover and bake in 10-minute increments. For a slightly drier top, uncover the foil and upper leaves carefully and bake another 10 minutes. Watch escaping steam.

Let stand 20 minutes before cutting into ten portions. Lift out with a wide spatula and remove banana leaves before eating. Refrigerate leftovers promptly in shallow containers and use within 3–4 days; reheat to 165°F (74°C).