How to Make It
Roast the poblanos over a gas flame or under the broiler, turning, until charred. Transfer to a bowl, cover tightly with plastic wrap and let cool. Peel the chiles. Using scissors, snip a slit in one side of each chile and remove the seeds, leaving the stem attached.
Preheat a grill pan. Brush the cactus with oil and grill over moderately high heat, turning once, until lightly charred and just softened, 4 minutes. Transfer to a work surface and let cool slightly, then cut into 1/2-inch dice.
In a large, deep skillet, heat the 2 tablespoons of olive oil until shimmering. Add the bell pepper, zucchini, chayote and a generous pinch of salt and cook over moderate heat, stirring occasionally, until the vegetables are softened and starting to brown, 15 minutes. Add the cactus, hominy, peas, raisins, apricots, oregano and cilantro and cook, stirring, until hot, 4 minutes. Season the filling with salt and pepper and let cool slightly.
Preheat the oven to 375°. In a bowl, combine all of the cheeses. Lightly season the insides of the poblanos with salt. Stuff the filling into the poblanos and press closed; arrange in a large baking dish. Pour the Spiced Walnut Sauce over the chiles and sprinkle the cheeses on top. Bake in the upper third of the oven for 10 minutes, until the cheese is melted and the filling is hot. Serve hot.
Cactus paddles are available at Mexican grocers. To clean, hold the paddle flat against a work surface with the thistle tips facing toward you. Using a sharp knife, shave off the thistles, working the knife away from you. Repeat on the other side.
Asadero (also known as queso quesadilla) and Oaxaca are great for melting. Cotija is a white, dry, crumbly cheese. All of the cheeses are available at Mexican markets.