Preheat your outdoor grill to high. Using a sharp knife or a mandolin, slice sweet potatoes into 1/4-inch slices. In a large bowl, toss the sweet potato slices with the olive oil and the vinegar. Add salt and pepper to taste. Grill slices of sweet potato for 5 minutes per side or until well-marked by the grill grates. Remove and cover.
In a large frying pan over medium heat, melt the butter and add the almonds. Cook until fragrant. Remove from heat and set aside.
Assemble the dish by shingling the sweet potatoes on a large platter and topping with the buttery almonds. Garnish with shallot and parsley. Squeeze lemon over the dish and season with salt and pepper to taste.