Try choosing sweet potatoes that have white flesh and light colored skins as opposed to bright orange ones because the latter contains more moisture when baking for crispy fries.
I too prefer baked to deep fried (for health reasons) and suggest making sure the wedges you cut are uniform in size, and use a cooking spray rather than coating with oil, use a high oven (I use 400-450) and...keep an eye on them with the extra fast heat. Turn when half done. I put them on a silpat for ease of turning etc.
I found that using a scant amount of vegetable oil (not olive) does the trick for making them browned and crispy. I use just enough to barely coat the fries and the baking sheet (metal). I rotate them 1 or 2 times during the baking, which takes about 30 minutes at 375.
"baked 'french fry style'" is an oxymoron. To properly cook "fries" you don't bake them. You deep fry them in oil---twice. Heat your oil to 375F. Add the fries to the oil and cook for 3 minutes, watching the color. Scoop them out with a spider or slotted spoon and allow to rest for two minutes. Plunge them back into the oil for another two minutes or until they look like fries. Drain, season and serve.
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http://www.food52.com/recipes/1691_southwestern_spiced_sweet_potato_fries_with_chilicilantro_sour_cream