Classic Austrian open sandwich: thick dark sourdough rye bread slathered with seasoned alpine curd cheese (Kräutertopfen), paper-thin radishes, snipped chives, and sea salt flakes.
In a bowl, mix the Topfen curd cheese with the sour cream, salt, black pepper, and sweet paprika until smooth and spreadable.
Slather each thick slice of rustic Austrian sourdough bread with an ample, thick layer of the seasoned curd cheese.
Layer the thinly sliced crisp radishes in an overlapping pattern across the top of the cheese spread.
Scatter heavily with fresh snipped chives, sprinkle with flaky sea salt and cracked black pepper, and serve immediately.