Make the stout aioli: Combine the stout, honey, brown sugar, ancho chile and dried cherries in a small saucepan and bring to a boil. Reduce the heat and simmer until the liquid is reduced to about 3/4 cup, about 15 minutes. Strain into a bowl, reserving the cherries. Let cool, then combine 1/4 cup of the liquid with the mayonnaise and refrigerate until ready to use. (Save the remaining liquid; it's a great glaze for grilled meat.)
Make the pickled red onion: Combine the malt vinegar, brown sugar and 1 teaspoon salt in a small saucepan; bring to a boil, then let cool 10 minutes. Place the red onion in a small bowl and pour the vinegar mixture on top; cover and refrigerate at least 30 minutes and up to 2 hours.
Meanwhile, make the corn relish: Preheat a grill to medium high. Brush the corn and poblano with olive oil; grill, turning occasionally, until charred. Slice off the corn kernels; seed and chop the poblano. Combine the corn, poblano, tomato and cilantro in a bowl; season with salt and pepper.
Make the burgers: Toast the coriander seeds and mustard seeds in a dry skillet over medium heat, about 3 minutes. Crush the seeds in a spice grinder or with a mortar and pestle and combine with the ground chile, 1 teaspoon salt and 1/2 teaspoon pepper. Chop the reserved cherries from the stout aioli. Combine the ground beef, bratwurst, 1 tablespoon of the seasoning mixture and the cherries in a large bowl with your hands. Form the mixture into four 3/4-inch-thick patties. Brush the burgers with vegetable oil. Sprinkle both sides with the remaining seasoning mixture.
Grill the burgers until slightly charred on the bottom, 3 to 4 minutes. Flip and grill about 4 more minutes for medium. Top with the cheese; cover and cook until melted, about 1 minute. Spread the stout aioli on the top and bottom buns. Sandwich with the burgers, corn relish and pickled red onion.
Photograph by Ryan Dausch
Courtesy of Food Network Magazine