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
Recipe courtesy of Joanne Hoff for Food Network Magazine