Using the large holes of a box grater or a food processor fitted with a grating disk, grate the potatoes and squash into a large bowl. You should have about 4 cups (400 g) total. Grate the onion into the bowl the same way. Mince or discard any large onion pieces. Stir in the eggs, flour, salt, baking powder, and Tabasco.

Line 2 or 3 baking sheets with paper towels. Have the prepared pans, the latke batter, a large spoon, and a spatula near the stove. Heat 1 or 2 large skillets over medium heat. Generously film the pan(s) with vegetable oil (not more than ¼ inch/6 mm deep). When the oil is shimmering in the pan (a tiny bit of batter dropped into it should sizzle on contact), start spooning in the latke batter by the level tablespoon, making sure to add both solids and liquid. Flatten each spoonful with the back of the spoon into a circle 2 to 3 inches (5 to 7.5 cm) in diameter. Do not crowd the latkes in the pan. You’ll get 6 to 8 mini-latkes in a 12-inch (30.5-cm) skillet. If making large latkes, use twice as much batter for each latke and cook only 4 or 5 latkes in the pan(s) at a time.

Cook the latkes, flipping them once, until golden on both sides, about 5 minutes total. Transfer the latkes to a prepared baking sheet. Cook the remaining batter in the same way, always stirring the batter before adding more to the pan and adding oil as needed to the edge of the pan. The latkes can be made a few hours ahead and reheated in a single layer on baking sheets in a 350°F (180°C) oven.

To serve, arrange latkes in a single layer on a platter and top each latke with a dollop of labneh, a dab of harissa, and a little finishing salt. Or, pile latkes on a platter and accompany with bowls of self-serve condiments.