We first made these potatoes last Fourth of July, and we keep making them to universal acclaim. The new potatoes we had included a red and white mix, and we added heirloom small blue potatoes (cut in half or thirds). The result we called Red, White, and Blue Potatoes, but the true genius behind the concept is Adam Perry Lang. He made the dish as an alternative to the usual boiling process, and the recipe is on page 341 of his book, Serious Barbecue.
The other great aspect of this recipe is the preparation time: almost none. Plus, you put the covered foil container it cooks in on the grill and leave it alone for an hour. Nothing more to do until you are ready to serve! By the way, disposable aluminum lasagna pans like the ones restaurants use for large carry-out orders work great for this recipe. The cooking method reminds us of the old Jiffy Pop® popcorn: all the free water in the foil converts to steam, so be careful opening the foil.
For those concerned about the amount of butter, we use half the butter called for in the recipe with excellent results. Likewise, cut back or omit the red pepper flakes if you fear it will be too spicy for your taste. Kosher salt will substitute for the fleur de sel without any problem in the taste.
2 lbs. thin-skinned, golf ball-size new potatoes, as similar in size as possible, scrubbed well
8 Tbsp (4 oz.) unsalted butter, cut into 1/2-inch cubes
1 Tbsp Old Bay Seasoning
1 tsp crushed hot red pepper flakes
5 thyme sprigs
¾ cup dill sprigs. large stems removed, about 10 sprigs
1 Tbsp coarsed ground fresh black pepper
1 cup water
fleur de sel
1. Lay two sheets of heavy-duty aluminum foil, each 16 to 18 inches long, on top of each other, and fold up the sides, creating a bowl shape with a rounded base about 9 inches across.
Place the potatoes in the foil bowl. At this point, they should be in a snug even layer. Top with the butter, Old bay, pepper flakes, thyme, ½ cup of the dill, and black pepper. Pour in the water. Gather the sides of the foil bowl, bringing them together to create a sealed rounded packet about 6 to 7 inches across.
2. Place directly on hot coals and cook for 20 to 30 minutes or cook in a 350℉ barbecue for about 1 hour to 1 hour 15 minutes, or until tender when pierced with a paring knife.
3. Carefully open the packet and transfer the potatoes to a serving bowl, removing the cooked herbs.
Garnish with the reserved ¼ cup of dill. Serve with the mustard and fleur de sel on the side.