Heat canola oil in a large nonstick skillet over medium-high. Add chopped leeks, salt, and pepper; cook, stirring often, until leeks are tender, about 4 minutes. Remove skillet from heat; transfer leeks to a large bowl, and let cool 5 minutes. Do not wipe skillet clean.

Add mashed potatoes, beaten eggs, flour, cheese, and parsley to bowl with leeks, and gently fold together until well blended. Return skillet to medium-high, and heat 2 tablespoon olive oil. Drop 3 to 4 (1/4-cupfuls) of potato mixture into hot oil in skillet, and, using a fork, gently flatten into 3-inch pancakes. Cook pancakes until golden brown and lightly crisp, 2 to 3 minutes per side, adjusting the heat to medium if needed to keep from over browning. Transfer to a plate lined with paper towels. Repeat with remaining potato mixture and, adding as needed, olive oil, to make 16 pancakes. Serve topped with crème fraîche. Garnish with parsley.