Put the potatoes, onion, garlic, eggs, potato starch, baking powder, salt, and pepper in a food processor. Process for about 30 seconds to combine the ingredients well. The texture will be grainy. Stir or briefly pulse in the scallions.
Heat about 3 tablespoons oil in a large, nonstick skillet over high heat. When it is hot, add about 1/4 cup batter, spreading it out to form a pancake about 4 inches in diameter. Repeat this to have 4 pancakes cooking side by side in the pan. (If using a smaller pan, make multiple batches.) Cook the pancakes for about 3 minutes on each side over medium to high heat, fiddling with the heat as needed to make sure they don’t burn before they cook through. They should be well browned and not squishy in the middle—you want to be sure the onions in the batter have a chance to cook through and lose their raw taste.
Transfer the pancakes to a wire rack so they don’t get mushy on the underside. Continue making pancakes until all the batter is used, adding more oil to the pan as needed. Serve. (The criques are best fresh from the pan but can be made 1 to 2 hours ahead and reheated on a baking sheet in a 425° F oven for about 5 minutes before serving.)
To make the salad, toss the greens in a bowl with the olive oil, vinegar, and salt and pepper to taste. Divide among four plates and arrange the criques on top.