Sauce:
- 1 cup finely chopped unpeeled English hothouse cucumber
- 3/4 cup mayonnaise
- 3 tablespoons prepared white horseradish
- 2 tablespoons finely chopped fresh Italian parsley
- 1 tablespoon finely chopped fresh chives
Fish cakes:
- 3 tablespoons olive oil plus more for frying fish cakes
- 3 medium carrots, peeled, finely chopped
- 1 2/3 cups finely chopped leeks (white and pale green parts only)
- 2 large eggs
- 6 tablespoons unsalted matzo meal
- 1 3/4 teaspoons coarse kosher salt
- 3/4 teaspoon ground white pepper
- 18 ounces skinless whitefish fillets, cut into 1-inch cubes
- 1 9-ounce skinless salmon fillet, cut into 1-inch cubes
- Lemon wedges
- Fresh Italian parsley sprigs
For sauce:
Step 1
Stir cucumber, mayonnaise, horseradish, parsley, and chives in medium bowl to blend. Season sauce to taste with salt and pepper. DO AHEAD: Sauce can be made 1 day ahead. Cover and refrigerate.
For fish cakes:
Step 2
Line large rimmed baking sheet with plastic wrap. Heat 3 tablespoons oil in heavy large skillet over medium heat. Add carrots and leeks. Saut&#;233 until soft but not brown, about 15 minutes. Cool in skillet.
Step 3
Beat eggs, matzo meal, coarse salt, and white pepper in large bowl to blend. Stir in carrot mixture. Place whitefish and salmon cubes in processor. Using on/off turns, chop fish to coarse paste (small pieces of fish will remain). Stir fish into matzo meal mixture.
Step 4
Using wet hands and about 1/3 cup for each, shape fish mixture into sixteen 1/2-inch-thick cakes. Arrange on prepared baking sheet. DO AHEAD: Can be made 1 day ahead. Cover with plastic and chill.
Step 5
Add enough oil to 2 heavy large skillets to coat bottom. Heat oil over medium-high heat. Add 8 fish cakes to each skillet. Sauté until golden and cooked through, about 3 minutes per side. DO AHEAD: Can be made 2 hours ahead. Transfer to another baking sheet, cover, and refrigerate. Rewarm uncovered in 350°F oven 10 minutes.
Step 6
Arrange 2 fish cakes on each plate. Spoon sauce over or alongside. Garnish with lemon wedges and parsley.