In a small bowl, combine shallots and apple cider vinegar. Let set 2-3 minutes to let flavors combine. Then whisk in mustard, olive oil and a pinch of kosher salt and pepper.
In a large skillet, cook chopped bacon over medium heat until crispy. Remove bacon from skillet and set on a paper towel lined plate to drain.
Remove all but 2 tablespoons of bacon drippings from pan, pat thinly sliced chicken breasts dry and season with salt and pepper. Cook chicken breast in skillet over medium heat until golden brown on both sides and cooked through. Set chicken aside to cool.
Whisk remaining pan drippings into dressing, taste and season with additional salt and pepper as needed. Once chicken has cooled, slice.
Assemble salad. In a large bowl, toss romaine lettuce with half of dressing. Then arrange remaining ingredients on top of lettuce. Top with remaining dressing, salt and pepper and a sprinkle of fresh chives.