In a small saucepan, bring the vinegar, ½ cup of water, sugar, salt and peppercorns to a boil over medium heat, stirring until the sugar and salt dissolve.
Remove from heat, separate the cucumbers and add to an airtight container then pour the vinegar mixture over the top. Add ½ cup of ice to rapidly cool the pickles for use. Cover and refrigerate for up to 2 weeks and drain before using.
For the chicken salad:
In a large mixing bowl mix together the shredded chicken, mayonnaise shallot, lemon zest and lemon juice until fully incorporated, being sure to leave the chicken in chunks for texture. Stir in the tarragon, chives and parsley until combined. Season with salt and pepper.
Refrigerate until ready to use, letting the chicken salad sit at room temperature for 30 minutes before serving.
For assembly:
Arrange butter lettuce leaves on the top of the bottom slices of bread. Top with scoops of the chicken salad then top with the quick pickles and potato chips. Close the sandwiches then cut in half and serve.
Notes
Try swapping the sourdough for another artisan bread, brioche buns, or croissants. Choose something sturdy enough to hold the filling without getting soggy.