Peel Yukon Gold potatoes (they have lighter skin than Russet potato) and cut into large chunks. Place in a medium pot and cover with water. Bring to a simmer over high heat, add a generous pinch of salt, and cook until fork tender, 12-15 minutes. While potatoes cook, finely mince shallot and chives.

Line a mixing bowl with a clean kitchen towel that you don't mind getting dirty. Peel Russet potato and grate on large hole side of a grater onto towel. Gather corners of towel together, lift, and spin base of towel to wring out as much liquid as possible. Reserve bowl and wipe clean. Once oven is preheated, run it for ten minutes, then turn it off. (You'll be keeping cooked latkes warm in oven.)

Drain Yukon Gold potatoes in a colander and return to pot. Mash with potato masher or fork and sprinkle matzo meal over top. Add grated Russet potatoes, shallot, and liquid egg. Season with a pinch of salt and pepper and combine thoroughly.

Line a plate with a paper towel. Heat canola oil in a large non-stick pan over medium-high heat. Drop a morsel of potato mixture in: it should bubble gently when it hits oil. If nothing happens, allow more time to heat. If it pops and bubbles aggressively, turn down heat. Form 3" latkes using 1/4 cup potato mixture. Working in batches to avoid crowding pan, fry until well-browned, 4-5 minutes per side. Transfer to towel-lined plate. Keep latkes warm in oven between batches.

Place applesauce in mixing bowl used to remove liquid from potatoes. Heat a small pan over medium-high heat. Add butter and cook until it begins to brown and smell "nutty", 1-2 minutes. Immediately remove from burner and stir into applesauce. Mix horseradish (to taste) and half the chives (reserve remaining for garnish) into sour cream in a small mixing bowl. Season with a pinch of salt and pepper.

Serve horseradish cream and applesauce on the side of a platter piled with crispy latkes. Garnish with remaining chives. For maximum flavor, use both sauces on latkes at once.