This recipe is best cooked inside poultry, rather than baked separately as a side dish.
Line a baking sheet with several thicknesses of paper towels. Heat the olive oil in a medium skillet over medium heat. Add the pancetta, and cook until golden and crisp, about 6 minutes. Using a slotted spoon, transfer the pancetta to paper towels, and allow to drain.
Add the chopped onion and celery to pan, and cook until slightly softened, about 4 minutes. Add the thyme, salt, pepper, and Madeira; cook about 30 seconds. Remove from heat.
In a large bowl, toss the pancetta, onion mixture, rice, grapes, and almonds. Use to stuff turkey or hens just before baking. If not using immediately, store in the refrigerator, covered with plastic wrap, until ready for use.
This makes enough stuffing for an 18-pound turkey or 8 Cornish game hens.