Whisk together all Tzatziki Sauce ingredients in a medium bowl until smooth, being careful not to over mix.
Process all falafel ingredients except oil in a food processor until well mixed.
Form 24 small balls or patties and refrigerate for 20 minutes.
Fry in canola oil in large skillet for 3 to 5 minutes or until golden brown; drain on paper towels. Serve warm with Tzatziki Sauce. Falafel may also be placed on a baking sheet and brushed with foil; bake at 400°F for 20 minutes until golden brown and cooked through.
Optional assembly on flatbread or salad
Grill flatbread on both sides to warm.
Place walnut falafel on bread and smear with tzatziki. Garnish with chopped tomato, lettuce and cucumber. Top with chopped California walnuts and drizzle with walnut oil and olive oil, if desired.