Step 1- Cook the Vegan Bacon
Heat a large skillet over high heat. Once hot, add the vegan bacon and cook until browned and crispy according to the package instructions. Remove from the pan and set on paper towels to drain.
Step 2- Caramelize the Onions
Remove any excess oil from the pan, leaving about 2 to 3 tablespoons. Add the onions and sauté on high heat for 2 minutes, then reduce to medium-high and cook until the onions turn dark brown, about 5 minutes. Remove from the skillet and set aside.
Step 3- Assemble Each Sandwich
Spread 1/4 of the caramelized onion mixture on a slice of bread. Layer on the vegan Swiss cheese, pear slices, 2 slices of vegan bacon, and 1 ounce of plant-based brie. Top with another slice of bread.
Step 4- Butter and Grill
Butter the outsides of each sandwich with the softened vegan butter. Grill on medium heat until golden brown, about 3 minutes per side.
Step 5- Serve
Slice each sandwich in half and serve warm while the cheese is still melty.