Place 2 tablespoons of the unsalted butter, 2 tablespoons olive oil, small-diced onion, small-diced celery, small-diced red and yellow bell peppers, minced fresh flat-leaf parsley, capers, hot sauce, Worcestershire sauce, crab boil seasoning, 1/2 teaspoon kosher salt, and 1/2 teaspoon freshly ground black pepper in a large saute pan over medium-low heat and cook until the vegetables are soft, approximately 15 to 20 minutes. Cool to room temperature.