Mine are always crispy.
The first thing is to know about your potato options.
RUSSET POTATOES (brown) = High starch, high density, high amylose. The amylose bursts in heat releasing a gluey gel. But high amylose lets the potatoe absorb stuff like water, butter, etc, like a sponge. A grainy potato.
---- Used for baked potatoes. Can also be used for mashed potatoes or French fries.
YUKON GOLD POTATOES (yellow) = Medium starch, medium density, medium amylose. A fine textured, creamy potato.
---- Used for Boiled potatoes but are versatile and can be used for other things too - especially mashed potatoes or French fries. As a baked potato, they're kinda thick and heavy, not fluffy.
RED SKINNED POTATOES (red) = Low starch, low density, low amylose. The starch strands don't break down much in heat so they keep their shape.
---- Used for potato salad, soups, stews, and salads. Can also be used for other things too - especially mashed potatoes or French fries.
THE MINOR HEALTH ISSUES FOR POTATOES:
GREEN SPOTS - Greenish spots are due to sun exposure. If eaten in large quantity, illness can result, even if cooked. The toxin is Solanine.
EYE SPROUTS - Sprouts of any size, on the potato, are toxic. But many sprouts would have to be injested to cause sufficient poisoning for concern.
I like to use the Red Skinned or Yukon Gold potatoes for potato pancakes. They can't absorb the cooking oil as easily as Russets.
Another important thing is the right cooking oil. They will fry the best in a High Temperature oil like cotton seed oil. It cooks them more evenly and the pancakes will be harder to burn.
Btw, I never use flour.
Here's my recipee:
4 medium Potatoes -- about 2 pounds
1 medium Onion
1/2 cup chopped Scallions (dinner onions) -- chop up the green parts too
1 large egg -- room temperature and beaten
Salt
Freshly ground Peppercorns -- or just pepper
I saw garlic in your recipe so you could probably add that when you add the scallions.
PREP:
Scrub the potatoes, under cold water, then peel and rinse them. Coarsely grate the potatoes with a hand grater. If you use a food processor, be careful. The "coarse" grating is important for making crispy potato pancakes. I use the hand grater.
Coarsely grate the medium onion and put in a separate bowl.
Put the grated potatoes in a large food strainer over a large bowl. Mash them down firmly with your hands. Now wrap them in cheesecloth or a clean dish towel. Wring them over the bowl as hard as you can and get all the water out. When you think all the water is gone, wring them some more.
Look in the bowl. All the starch is at the bottom of the bowl with a layer of water over that. Very carefully pour off that water and leave only the starch.
Now put the potatoes in the bowl with the starch and add the grated medium onion. Mix that all up. Now add the chopped scallions (and optional chopped garlic) and the beaten egg. Salt and pepper the mixture then mix it all up.
COOKING:
Set the griddle or burner to medium heat. Add a thin film of oil to the griddle or skillet. Now make sure the heat is at the right setting. To test it, put a pinch of the mixture on the griddle or skillet. When the oil is hot enough to make it sizzle, then it's hot enough so leave it at that setting, no higher.
Btw, this recipe is for thin pancakes.
Now put 2 tablespoons of the batter on your hand. Flatten and shape it into a cake and put it on the griddle or skillet. Use a big spatula to keep it flat while it cooks. Fry it for about 3 minutes (till golden) on one side. Then flip it over and do that again, for the other side. Put it on paper towels and serve them hot.
Imo, when you added the sauteed onion and fried garlic, the grated potatoes soaked up so much oil that they couldn't get crisp. Frying a soggy mixture would just transfer the heat through the potatoes evenly. The outside needs to fry faster to make them get crisp.
So while the heat went through the mixture evenly, the outside couldn't get hot enough to fry.