For the burger patties: Form the ground beef into six patties and sprinkle with the salt and pepper.
In a bowl, mix together the chorizo and the panko and form into six patties.
Heat a large cast-iron skillet over high heat until smoking. Coat the pan with 1 tablespoon of the grapeseed oil, and then place three burger patties in the pan. Reduce the heat to medium-high and cook until the patties are seared on the first side. Flip, and cook on the reverse side until the sausage patties are cooked through and the beef patties have reached the desired doneness. Remove the patties from the pan and repeat, adding another tablespoon of oil for each batch, until all the patties are cooked. Allow the burgers to rest for 5 to 10 minutes before plating.
For the fajita-spiced peppers and onions: Heat a large saute pan over high heat until it begins to smoke. Reduce the heat to medium and swirl in the grapeseed oil. Add the peppers and onions and saute until tender.
In a small bowl, mix together the chili powder, oregano, coriander, salt, cumin, black pepper and cayenne until well blended. Add the spice mixture to the peppers and onions and cook, stirring, for 2 to 3 minutes.
For the corn salsa: Combine the corn, crema, red onions, poblanos, cilantro, honey and lime juice in a bowl and mix well. Season with salt and pepper to taste.
To plate: Butter the insides of the burger buns and toast, cut-side down, in a hot skillet.
Place a tomato slice on each bottom bun; then layer with a beef patty, some peppers and onions, a sausage patty and some corn salsa. Top with a top bun, and serve with French fries.