Bring a small skillet of salted water to a boil over medium-high heat. Add the trimmed asparagus spears and blanch for 2 to 3 minutes until they turn bright green and are tender-crisp.

Immediately transfer the asparagus to a bowl of ice water to stop the cooking process, then drain and pat dry with paper towels.

In a small mixing bowl, whisk together the sour cream, prepared horseradish, fresh lemon juice, and chopped dill. Season the mixture with a pinch of salt and black pepper to taste, adjusting the horseradish if you prefer a sharper kick.

Lightly butter each slice of dark rye bread, spreading it evenly to the edges. This classic technique adds rich flavor and prevents the bread from getting soggy from the toppings.

Drape the smoked salmon slices evenly over the buttered rye bread, creating a rustic, ruffled layer on each slice. Slice the blanched asparagus spears in half lengthwise or crosswise, and arrange them neatly on top of the salmon.

Dollop a generous spoonful of the prepared horseradish cream over the asparagus on each sandwich. Garnish with additional fresh dill sprigs, a crack of black pepper, and serve immediately alongside lemon wedges for squeezing.