Whisk horseradish into crème fraîche and add salt to taste. Chill at least 1 hour.
Heat oil in a large frying pan over medium-high heat. Add onion and cook, stirring often, until golden brown, 8 to 10 minutes. Add salt and pepper to taste. Let cool.
Mound a spoonful of onion on each chip; top with a dollop of horseradish crème fraîche and some salmon roe. Serve immediately (see tip above).
Note: Nutritional analysis is per chip.