Glazed Sweet Potatoes with Maple Gastrique

Taste was good, but labor intensive and based careful measurement on proportions given gastrique failed to thicken--at all. Given fact it did not thicken, it provided no coating to potatoes and ended up a broth under them as they cooked. I did cook the dish far longer than 4 minutes, testing for tenderness to judge how long (about 25 min with potatoes I used). I would want to know how to fix the thickening issue before I'd make again. 

Yes, I made it this past Thanksgiving and the 4 minutes in the oven was enough. Just boil until almost cooked through. In fact, you could probably cook through entirely in the boiling water but mine was just slightly underdone in the middle. The short time in the oven was enough to finish them off!

can I make this dish the day before

This is an excellent recipe, one I'll make over and over.  However, who would ever turn on an oven to 400 degrees to bake something for only 4 minutes???  Will the author please recheck that baking time?  I baked mine about 15 minutes and they turned out wonderful.  Also, you don't need that much salt at the end.  One sprinkling is fine.  

I made this dish with Murasaki sweet potatoes, which I wouldn't recommend, because the potatoes are white, which isn't as pretty, and they crumble more like a Russett potato, which makes it hard to arrange them in the dish.  The maple gastrique is simple to make, so I made it on a weeknight.  The vinegar /potato combination is reminiscent of warm German potato salad, only with maple flavor.  Rounded out with other dishes, this makes a nice addition to Thanksgiving or any meal.  I followed the recipe as written except that I didn't add the fresh marjoram leaves at the end.

Is this correct that you only bake these potatoes for 4 minutes at the end? I know they're boiled in Step 2 but is this enough to soften them completely?