Peel the potatoes while they are hot, place in a bowl which has been well rubbed with garlic. Let them stand till cool. Slice the cucumbers, and add salt and pepper. Slice the cooled potatoes and pour heated bacon fat over them. Combine with the cucumbers and onion and toss lightly. Add the oil and vinegar, and again toss lightly. Let stand 2 hours before serving. Add more oil and vinegar, if needed. Arrange on a bed of greens and sprinkle with a touch of paprika.