Preheat oven according to package directions for puff pastry shells. Arrange shells on a non-stick baking sheet then place in oven. Bake until golden, remove from oven and let cool.
Place a large deep-sided skillet over medium-high heat with 2 turns of the pan of EVOO, about 2 tablespoons. Add celery, onions, carrots, bay leaf and season with a little salt and pepper.
Cook, stirring frequently, for about 5 minutes, until the veggies start to get tender. Add the red bell pepper and continue to cook for an additional 2-3 minutes. Scoot the veggies over to the sides and add the butter to the center of the skillet. Once butter has melted, add flour and cook for about a minute.