Slice the pork tenderloin into 6 to 7 medallions that are 1/2-to 3/4-inch thick, depending on the shape of the tenderloin.
Combine the salt, coriander, fennel and pepper in a small bowl and mix well.
Spread the sliced pork medallions on a plate or baking sheet and season evenly on both sides with the salt mixture (you may not use it all).
Spread the flour on plate. Dip each of the pork medallions in the flour and pat off any of the excess.
Heat a large cast-iron skillet or heavy-bottomed pan over medium-high heat. Add the olive oil and 1 tablespoon of the butter. Cook the pork medallions in batches, adding more oil and butter as needed, browning them well on both sides, about 5 minutes total. Remove to a rack to rest. It's ok if the pork is not cooked all the way through at this stage, it will finish cooking in the sauce.
When all the pork has been browned, pour off the fat in the pan into a small bowl. Add the remaining tablespoon butter and melt over medium-high heat. Add the shallots, thyme sprigs and some salt to the pan and cook until the shallots are softened and starting to get a little color, about 1 minute. Then add the apples and saute, stirring occasionally and adding more butter if necessary, until tender, 2 to 3 minutes more.
Remove the pan from the heat, add the bourbon and stir to cook off some of the alcohol. Return the pan to the heat and cook, stirring, until reduced by half. Remove the thyme sprigs. Return the pork to the pan along with the chicken stock and season with salt. Simmer until well thickened and reduced, 2 to 3 minutes. Spoon the pork and apples onto plates and drizzle with the sauce.