Put the potatoes in a large pot and cover with lightly salted water. Cover and bring to a boil. Uncover and boil until tender when pierced with the tip of a knife, about 10 to 15 minutes. Drain and let cool.
Heat the olive oil or butter in a saucepan over medium heat. Add the leek and sauté until limp. Add garlic and cook until fragrant but not browned. Pour in the cream, reduce heat to med-low and cook, stirring occasionally, until slightly thickened and reduced, about 15 minutes. Stir in the nutmeg and seas with S&P. Remove from heat and let cool.
Cut the cooked potatoes into 1/4-inch slices and toss together with the cooled cream and herbs.
Lay 1 phyllo sheet on a flat work surface. Keep other sheets covered with waxed paper and damp towel to prevent from drying out. Brush lightly with melted butter and sprinkle with 2 tsp bread crumbs. Top with a second sheet, brush with the melted butter and sprinkle with 2 tsp bread crumbs. Repeat with remaining sheets, bread crumbs and most of the remaining butter to create a single stack. Spoon the potato mixture in a strip down a long side of the phyllo, positioning it 2 inches from the edge. Fold the uncovered edge over the filling and roll the phyllo around the filling as you would a jelly roll; pinch the ends closed. Place the strudel, seam side down, on a parchment-lined baking sheet and brush lightly with the remaining butter. Bake until golden brown and the filling is hot and bubbly, just about 30 minutes. Let cool for a few minutes then cut with a serrated knife. Slice on the diagonal into 8-10 slices and serve immediately.