In a large bowl, combine the grated potatoes and finely chopped onion.
Add the flour, egg, baking powder, salt, and black pepper. Mix well until the ingredients are evenly combined.
If using, fold in the cooked and crumbled bacon or sausage.
Heat oil in a large skillet over medium heat.
Spoon heaping tablespoons of the potato mixture into the hot oil, flattening them slightly with the back of the spoon.
Fry until golden brown and crispy on both sides, about 4-5 minutes per side.
Transfer the cooked blynai to a plate lined with paper towels to drain excess oil.
Enjoy your meal!