In a small bowl mix together paprika and curry powder, set aside.
Place 2 breasts on large sheet of plastic wrap, cover with more plastic and pound with a mallet until they are about 1/4-inch thick. Repeat with remaining breasts. Sprinkle spice mixture on chicken breast, rubbing to coat (Chicken may be wrapped and refrigerated for up to 12 hours.)
Preheat oven to 200 degrees. Season chicken on both sides with salt. In a large skillet over medium-high heat, add enough canola oil to film the bottom of pan. Working in batches, without crowding, place breasts smooth side down and let cook until golden brown, 1 to 1 1/2 minutes. Turn and cook for another 1 to 1 1/2 minutes. Transfer to a baking sheet and keep warm in oven.
Wipe out skillet and return to medium heat. Add 1 tablespoon of butter and shallot/onion, and sauté for 30 seconds, swirling pan to coat shallot/onion with butter. Pour in wine, raise heat to medium-high, and cook until wine is reduced by half, about 1 minute. Add stock, bring to boil, and cook until reduced and slightly thickened, 1 to 2 minutes.
Stir in chopped tarragon, remaining 2 tablespoons butter, and any juices that have accumulated on baking sheet. Swirl to melt butter, and season to taste with salt and pepper. Arrange chicken on a warmed platter, pour sauce over it, and garnish with whole tarragon leaves.