Step 3: In a medium bowl, add the arugula. Add the olive oil, red wine vinegar, salt and pepper. Toss with your hands or salad tongs until arugula is evenly coated. In a small bowl, mix together mayonnaise, lemon juice and horseradish. Slice the french baguettes in half. Spread a little mayonnaise on each half and toast in a pan on medium-low heat.