1. Pre-heat the oven to 140C. For the reduction, place all ingredients in a saucepan and reduce until there is around 100ml of liquid remaining. Remove from the heat, pour into a large mixing bowl and set aside to cool.
2. For the terrine, begin by lining the terrine mould with baking paper, leaving plenty of excess around the edges to cover the completed terrine. Then, line the mould with the pancetta or bacon by laying slices side by side, leaving plenty of excess over the sides (to cover the mince mixture).
3. Combine the terrine ingredients with the reduction in a mixing bowl and season well with salt and pepper. Check the mixture is seasoned correctly by making a small patty and frying it in a pan so you can taste it. Press the terrine mix into the lined mould, close with the excess pancetta or bacon and the baking paper and press down gently. Cover the terrine mould with a lid if you have one, otherwise use tinfoil.
4. Place the terrine in the oven and cook for about 1 hour. Check the terrine is cooked by pricking it with a small knife and seeing if the juices run clear. If the juices are still pink, cook for a little longer, keeping a close eye to make sure it doesn't overcook. Remove from the oven and allow to cool slightly before refrigerating overnight, still in the mould.
5. For the chutney, place the onions, garlic, ginger, sugar, vinegar, cloves and salt in a small pot and cook on medium heat until the mixture has reduced to thick syrup.
Add the chopped tamarillos to the reduction and stir well. Continue cooking for 5 minutes then remove from the heat and set aside to cool. Transfer to a bowl or container, cover and store in the fridge until required.
6. For the crostini, preheat the oven to 200C. Place the sliced bread on a lined baking tray, drizzle with olive oil and sprinkle with salt. Bake in the oven for approximately 10 minutes, watching carefully to ensure they don't burn. Allow to cool completely and store in an air-tight container until required.
7. To serve, remove the terrine from the fridge (ahead of time is best so it's not too cold). Turn the terrine out on to a serving platter by gently pulling on the cling film or baking paper, scrape off any excess jelly and garnish with a little watercress if desired. Warm the chutney slightly and serve in a small bowl or serving dish. Serve in the centre of the table with plenty of the crostini on the side.