Grate potatoes, parsnips, and onion through large holes of a box grater; toss with lemon juice. Spread mixture onto 2 clean, dry kitchen towels. Roll up each towel, starting with 1 long side. Wring towels to squeeze out excess liquid. Place potato mixture in a large bowl.
Stir in eggs, matzo meal, salt, and pepper. (Mixture will by dry but will hold its shape when pressed together.)
Melt 2 Tbsp. butter with 2 Tbsp. oil in a deep electric skillet heated to 375° or in a large nonstick skillet over medium to medium-high heat. Drop 6 to 8 loosely packed 1/4 cupfuls potato mixture into hot butter mixture; press lightly to flatten into 3-inch rounds. Cook 3 to 5 minutes on each side or until golden brown. Drain on paper towels. Sprinkle with additional salt. Repeat procedure with remaining butter, oil, and potato mixture. Serve latkes immediately, or keep warm on a wire rack on a baking sheet in a 250° oven up to 30 minutes. Garnish, if desired.
Note: For testing purposes only, we used Manischewitz Unsalted Matzo Meal.