In a large skillet, heat 1 tablespoon oil over medium-high heat. Add mushrooms and cook until golden brown and tender, 10 to 15 minutes.
Add garlic, ¾ teaspoon salt, and red pepper; cook until garlic is tender. Add bourbon; cook until liquid has reduced by half. Add 3 tablespoons butter, stirring constantly to emulsify the sauce. Remove from heat and add chives and parsley.
In a large skillet, heat remaining 2 tablespoons butter and remaining 1 tablespoon oil over medium heat. Add onion and remaining ½ teaspoon salt; cook, stirring frequently, until onions are golden brown, about 30 minutes. Remove from heat and let cool.
Spread cheese evenly over bread slices. Top each with one-eighth of caramelized onions and one-eighth of mushroom mixture. Garnish with parsley and chives, if desired.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/bourbon-glazed-mushroom-toasts/