Preheat the oven to 375ºF. Arrange the bacon on a slotted broiler pan or a cooling rack set over a baking sheet and bake until crispy, 15-17 minutes. Cool the bacon and cut the slices in half. (Leave the oven on for toasting the bread.)

Using a 3-inch round cookie cutter, cut out rounds of bread (or trim 1 inch of crust all the way around the bread slices to form small squares) save the trimmings. Arrange the bread on a baking sheet.

Make the sliders: Heat a skillet or griddle over medium-high heat. In a large bowl, combine the turkey, grated onion (grate it right over the bowl so the juices fall into the meat), hot sauce and poultry seasoning, Dijon mustard (if using), season with salt and pepper and mix thoroughly. Score the mixture into 4 equal portions and form each portion into 2 patties slightly thinner at the center than at the edges for even cooking and to ensure a flat surface (burgers plump as they cook). Add the oil, 1 turn of the pan, to the hot skillet. Cook the sliders, turning once 6 minutes, or until the juices run clear.

While the sliders are cooking, lightly toast the bread rounds in the oven and make the avocado dressing. Purée the avocado flesh, sour cream, lemon juice, garlic, chives, dill and parsley in a food processor; season with salt and pepper.

Place the sliders on 8 toasts and top with crisscrossed bacon, lettuce, tomato, and avocado-ranch dressing. Set the top toasts in place.