Which oils or fats make the crispiest roast potatoes?

I think it's more about technique than what fat you use when you're looking for crispy outsides (I'm sure there is at least one question here already that has the technique answers).

About the only solid advice I would give is that you need to find a fat that tastes good to you, or is neutral if that's your preference, and make sure the one you use won't burn at the temperature you're using.

Beyond that, it's all about taste and technique.

edit: I looked for questions that might have solid technique answers, but didn't find any. So I looked out on the greater web and found some advice from Cook's Illustrated. Crisp Roasted Potatoes

It doesn't have the recipe for free, but the advice is good: Parcook at a fast simmer, get a little rough with the parcooked potatoes to rough up the outside, choose the right potatoes (they liked Yukon Golds).

The technique I've always used for roasting potatoes is:

• Preheat the oven to 200'C/395'F/Gas Mark 6
• Add quite a thick layer of your choice of oil (we use Extra Virgin Olive Oil) to a deep roasting tin/tray. Enough oil so that you can use the oil to baste the potatoes.
• Add the tray to the preheated oven.
• Parboil the potatoes for about 8/10 minutes in a saucepan of water
• Drain them off completely
• Put the lid back on the saucepan and shake the potatoes about little bit to rough them up
• Then add salt and shake a little more
• Take the roasting tray out of the oven and add the potatoes to the oil, which will be smoking hot by now. The potatoes will sizzle when you add them to the oil.
• Roasting them for 1 hour until golden brown and crispy.

I've heard that Goose Fat is very good for roasting potatoes, but I've always used Olive Oil and they always come out brilliantly.

During the fall, upon acquiring sacks of russets during the potato harvest, I have found that using deer fat works very well. The fat on the rear haunches, just above the tail of the deer can be quite thick, actually 3/4" - 1" in thickness, and a lot of it. It is pure white and renders clear, and I store that fat just like coconut oil. I soften up a 1/4 cup of it and rub it on my spuds. It promotes a very nutty, almost musky flavour to the cooked potatoes. After I prick my spud, I oil it real well with the deer fat, then wrap it in foil and let it cook for 40 minutes. Then I pull it out and rub more fat on it and slip it back into the 400 degree oven. After 30 more minutes the skin gets wrinkled a little bit and it acquires a smokey flavour. It goes really well with the deer ribs too, although there is a little bit of coating on your upper palate if you should happen to drink something cold.

I've had good luck by using duck fat (as it's been suggested in the comments above), and by also tossing the potatoes a bit after par-boiling them. I've found that gives extra fluff and crispness to the potatoes.

This recipe has a good of explanations of the mentioned techiques: http://mattikaarts.com/blog/vegetables/roast-potatoes-sauce-gribiche/

Part of the problem is keeping the fat on the potato. There are a few tricks that can help here (I'll skip the parboiled hint above):

• Wrap the potato in foil + oil until cooked, then place under the broiler for 10 minutes
• Use cold butter, and score potato (or cut slices into it): cold butter stays on the potato longer, and the slices/score marks help keep it on the surface longer
• Pan fry (or deep fry), then bake off the remaining time
• Marinate in oil overnight after washing + drying: a small amount of oil will remain in the skin, making it crispier
• Bake slowly (this encourages a more cooked exterior, for a given amount of interior doneness)
• Baste with oil every 15-20 minutes (this refreshes the oily exterior)
• Re-salt + season during the cooking process

Duck or goose fat is good for flavour, but any fat will do for crispiness. As bikeboy says, crispiness is down to technique.

Parboil for 6 minutes (i.e. 6 minutes once the water is up to the boil). Drain well, then put back on the heat for a few seconds to help steam out some more moisture; you want to dry the outside of the potatoes as much as possible. Put the lid on the pan and shake it around to break up the edges of the potatoes. This will allow them to crisp up nicely. If you want to go super-crispy, sprinkle a tablespoon or so of flour into the pan and shake around.

Roast in the oven, preferably nestled around the meat, until they're crispy, which should be about 1-1.5 hours depending on how hot you have your oven.

I would agree with bikeboy389 on it being a technique issues -- but one thing that hasn't been mentioned is that it's important not to pack them too tightly when roasting.

As with making home fries, you want the potatoes to be in a single layer, with space in between them so any moisture given off has space to evaporating without steaming the potatoes.

I don't know that the fat selection matters that much, so long as you don't choose something with such a low smokepoint that you end up smoking yourself out of the kitchen. (for crispiness, at least; for flavor, yes, it matters)

I use what is sold in the UK as "vegetable oil", which I believe is primarily rapeseed oil. This has a very neutral flavour, low water content, and can get very hot without smoking or boiling.

For crispness:

• heat the oil on its own in the oven
• use floury potatoes
• peel, and cut such that there are lots of pointy wedge shapes
• parboil for 10 minutes, drain and shake about to scuff up the surface
• place in the oil, and spoon hot oil on top too
• roast until crispy

This works for parsnips too; you can do parsnips and potatoes in the same pan.

Getting a good layer of starch on the outside of the potato will definitely up your crispness game by leaps and bounds, but focusing just on fat:

While any fat will get stuff crisp in the oven, foods will stay crisp better and feel more crisp when using a saturated fat. Since saturated fats are solid at room temperature, they will be firmer as the food cools, allowing the crispness to outshine the greasiness.

Here are some sources on potato roasting fats:

What Serious Eats has to say

Fine Cooking's two cents

A Chowhound Thread

Cool the potatoes in the fridge for about half an hour (longer if you have time) after the par boil process and then into hot vegetable oil .Important to note that the variety of potatoes makes a huge difference to the end product. Roosters or Maris Pipers will never fail with this and will be beautifully crispy on the outside.