Make your dressing first.

A simple remoulade can contain just the first 4 ingredients or you can keep adding more of what’s listed below. Of course add salt and pepper to taste.

1 cup mayonnaise (homemade preferable… watch out for it getting too salty if using store bought) 
2 Tablespoons of lemon juice or 1 Tbs lemon juice and 1 Tbs red or white wine vinegar
1 Tablespoon of mustard (whole grain or dijon or a combination)
1 Tbs chopped parsley

1 Tbs minced shallot
1 Tbs minced cornichon
1 Tbs minced capers
1 tsp minced tarragon
1 tsp minced chives
2 Tbs creme fraiche
Pinch cayenne pepper
1 tsp horseradish 
1 chopped hard boiled egg

Peel and julienne celeriac (using knife, mandolin or food processor) and toss with the dressing. If you add too much stuff, just add a bit more creme fraiche or mayonnaise to balance it out.