Set up a bowl of cold, salted water. Peel the potatoes and put them in the bowl of salted water as you grate them. Once they're all grated, drain the potatoes and place them in a sieve set over another bowl. Let them drain for a good 20-30 minutes. Press on the potatoes to squeeze out more liquid.
Transfer the grated potatoes to a bowl. Grate the onion, carrot, horseradish, and garlic into the bowl of potatoes and season the mixture with your favorite all-purpose seasoning blend or salt and pepper.
Preheat the oven to 275°F. Place a wire cooling rack into a baking sheet.
In a large skillet, heat a thin layer of canola oil over medium to medium-high heat.
Beat the egg and sprinkle in matzo meal or flour. Pour over the potatoes and vegetables and stir to combine.
Add a large spoonful of the potato and vegetable mixture into the pan and cook until nicely browned on both sides. Keep the pancakes warm in the oven as you make more pancakes.
In a small mixing bowl, mix together the sour cream and herbs.