Preheat the oven to 450°.
Wash and pat dry both tenderloins, season with salt and pepper and set aside. In a sauté pan large enough to hold both tenderloins add the oil and butter. Melt the butter over medium-high heat just until smoking. Brown both tenderloins on all sides. Remove the pork from the pan and finish cooking in the oven for 15 to 20 minutes or until you reach an internal temperature of 140°.
Deglaze the sauté pan with some of the ginger ale, scraping up all residual brown bits. Add the shallots and cook for a minute or 2 just until wilted and translucent. Stir in both the fresh and crystallized gingers and let cook for another 2 or 3 minutes. Add the rest of the ginger ale and let simmer until reduced by a third, about 5 minutes.
Finally, add the nuts and raisins, and stir in the heavy cream. Allow the sauce to cook and thicken for a few minutes. Season with salt and pepper, and serve the sauce spooned over the sliced tenderloin.