Preheat oven to 425°. Toss together first 4 ingredients in a large bowl; arrange mixture in a single layer in a lightly greased 15- x 10-inch jelly-roll pan. Bake 20 minutes or just until potatoes are tender, stirring after 10 minutes. Cool completely in pan on a wire rack (about 30 minutes). Stir in bacon and parsley.
Unroll piecrusts; stack on a lightly greased surface. Roll stacked piecrusts into a 12-inch circle. Fit piecrust into a 10-inch deep-dish tart pan with removable bottom; press into fluted edges. Trim off excess piecrust along edges. Line piecrust with aluminum foil or parchment paper, and fill with pie weights or dried beans. Place pan on a foil-lined baking sheet.
Bake at 425° for 12 minutes. Remove weights and foil; bake 5 more minutes. Cool completely on baking sheet on a wire rack (about 15 minutes). Reduce oven temperature to 350°.
Layer half of sweet potato mixture and half of cheese in tart shell; repeat layers once.
Whisk together half-and-half and next 3 ingredients; pour over cheese.
Bake at 350° on lowest oven rack 35 to 40 minutes or until set. Cool tart on baking sheet on a wire rack 15 minutes.