In a medium mixing bowl, combine the cream cheese, sour cream, lemon zest, lemon juice, dill, chives, garlic, grated cucumber, and bacon bits. Stir until smooth and evenly combined. Season with salt and pepper to taste.
Using a 2¾-inch cookie cutter, cut one round from each slice of bread.
Spread a generous amount of the cream cheese mixture onto one bread round, then top with another round to form a sandwich.
Serve as is, or for a decorative presentation, pipe a small dollop of the filling onto the top of each sandwich. Place a cucumber slice on top.
Pipe an additional small dollop of filling onto each cucumber slice. Garnish with fresh dill and a sprinkle of bacon bits.
Notes
Larger sandwich bread or brioche may yield slightly bigger rounds.
Save bread scraps for breadcrumbs or croutons.
Sandwiches can be made a few hours ahead and stored in an airtight container in the refrigerator.