If you can't find sweet, crunchy jicama, you can substitute red radish slivers or mung bean sprouts.
Heat 1/2 tablespoon of the oil in a large nonreactive skillet. Add half of the chicken livers in a single layer, season with salt and pepper and cook over high heat, turning once, until well browned and medium-rare to medium, about 2 minutes per side. Add 1 tablespoon of the Marsala and cook until reduced to a thin glaze. Transfer the livers to a plate. Repeat the process with the remaining 1/2 tablespoon oil, remaining livers and 1 more tablespoon of the Marsala. Reduce the heat to moderately high if the livers start to burn.
Melt the butter in the skillet. Add the shallots and cook over moderate heat, stirring, until softened, about 4 minutes. Increase the heat to moderately high, add the remaining 1/4 cup Marsala and boil, scraping the skillet to loosen any browned bits, until reduced by half, about 1 minute. Add the tomato paste and boil until slightly thickened, about 2 minutes.
Return the chicken livers to the skillet and season with the tarragon, lemon juice, salt and pepper. Simmer to heat through, then transfer to a platter. Scatter the jicama sticks on top and serve.
Serve With: Buttered fettuccine or wide egg noodles.