Preheat the oven to 400˚F and line a baking sheet with parchment paper.

Set aside two tablespoons pepitas for garnish. Finely grind the remaining pepitas and peppercorns together in a spice grinder until reduced to a meal consistency.

Place the eggplant and tomatoes on the baking sheet. Drizzle with a little olive oil. Place the garlic cloves on a small piece of foil, drizzle with oil, and wrap. Add them to the baking sheet. The total amount of olive oil used is about 1 tablespoon. Roast the vegetables until the skin of the eggplant is charred and the tomatoes and garlic are very soft, 40 to 50 minutes.

This next step involves puréeing about three cups of sauce in the bowl of a food processor fitted with a blade. (A blender can also be used.) Depending on the size of your equipment, you may need to do this step in batches. Slice the eggplant in half, remove the long strands of seeds, and discard. Scoop out the flesh using a spoon, and place in the bowl of a food processor. Remove any stems from the tomatoes, and slip off any skins easily removed. Add the tomatoes to the food processor bowl. Remove the skins from the garlic cloves, then coarsely chop the garlic and add to the bowl. Add the white onion, serrano pepper, ¼ cup of the broth, vinegar, and salt. Whirl like crazy until the sauce is smooth.

Pour the sauce into a medium saucepan and simmer over medium-high heat, stirring frequently, until thickened and reduced to roughly two cups, 15 to 20 minutes. Heat 2 tablespoons olive oil in a large frying pan over medium heat. Add the ground pepita mixture and stir constantly until it darkens in spots and becomes a coarse paste, about 10 minutes. Stir in the eggplant sauce and remaining 1¼ cup broth. Simmer until thick, about 5 minutes. Add seasoning or additional vinegar to taste.

Line a baking sheet with parchment paper. Lay the peppers on the sheet and broil until completely blackened and soft, turning as needed. Place in a container or bag to steam; peel, seed, and coarsely chop.

Heat a dry frying skillet over medium heat and add the mushrooms. Cook for 15 minutes, occasionally moving around, until the mushrooms release their moisture and the liquid evaporates. Add the butter to the skillet and sauté the mushrooms for about 1 minute. Add the peppers and sauté for 1 minute. Season with salt and pepper to taste.

Bring the broth, milk, salt, and mustard to a very low simmer in a medium saucepan over medium-high heat. Stir in the polenta and cook until smooth and no longer crunchy, 20 to 30 minutes, stirring frequently. Stir in the cheese and butter. Immediately spoon onto a plate or into a shallow bowl. Spoon the mole sauce over and top with the roasted peppers, mushrooms, parsley, and reserved pepitas.