For the filling: Preheat a grill to medium-high heat.
In a bowl, toss the poblano peppers with the canola oil. Place on the grill along with the scallions and corn and cook, turning occasionally, until the vegetables are nicely charred.
Immediately place the peppers in a bowl, cover with plastic wrap and let sit for 10 minutes to sweat and soften. Chop the charred scallions and put them into a large bowl. Cut the corn kernels off the ear and add to the bowl. Peel the skins off the peppers, finely chop and then add them to the corn and scallions. Stir in the goat cheese and Parmesan.
Heat a large saute pan on the grill, add the chorizo and cook until the oils are released and the chorizo is slightly browned, 3 to 4 minutes. Add the chorizo to the poblano-cheese mixture and gently fold together. Set aside until ready to use.
For the arepas: Combine the masa flour and salt in a large bowl. Pour in 2 1/2 cups hot water and, using a wooden spoon, stir to combine. Add in the melted butter, cover with plastic wrap and let rest for 10 minutes.
Divide the dough into 12 small balls. Place each ball in between two pieces of plastic wrap and flatten using a heavy-bottomed skillet or tortilla press to about 3 1/2 inches in diameter and 1/4 inch thick.
Heat the canola oil in a cast-iron skillet over medium heat. Fry the arepas until lightly browned--they should have a nice crust on the outside but still be soft inside--about 5 minutes per side.
Using a sharp knife, slice the arepas in half, similar to an English muffin. Stuff 1 to 2 teaspoons of the filling inside each. Garnish with some chopped cilantro and a squeeze of lime juice.