1. Preheat the oven to 400˚. Arrange the avocados on a baking sheet and drizzle with 2 tablespoons of the olive oil. Season generously with the salt, pepper and cumin seeds and toss until nicely coated. Roast until the avocados are lightly browned, about 15 minutes.
2. Meanwhile, on a large baking sheet, arrange the tortilla chips in a single layer and scatter the cheddar, pine nuts and pumpkin seeds over the top. About 4 minutes before the avocados are done roasting, place the large baking sheet in the oven to melt the cheese and toast the nuts and seeds.
3. In a large bowl, toss the salad greens and watercress with the lemon juice and remaining 6 tablespoons olive oil. Season with salt and pepper.
4. Remove the avocados and tortilla chips from the oven. Divide the chips among 4 plates. Slice the avocados and divide them among the plates. Scatter the greens over the top and garnish with the chiles. Serve immediately.