Preheat oven to 350°.
Heat oil and butter in a large, oven proof dutch oven over medium high heat.
Season ribs lightly with salt and pepper. Toss ribs and flour in a bag to coat.
Sear ribs on all sides. About 10 minutes. Transfer ribs to a platter and set aside.
Add the carrots, celery and shallots to the pot. Sautee about 10 minutes until they start to caramelize.
Add the garlic and cook 2 minutes longer. Stir in tomato paste, brown sugar and Worcestershire sauce. Cook for 2 minutes more.
Deglaze the pot with ½ cup Irish whiskey scraping up an brown bits from the bottom. Allow whiskey to boil until reduced by half. Add the beef broth, salt and pepper.
Return ribs and any juices to the pot and arrange so they are covered. Add the thyme, cover and cook in the oven 2 - 2 ½ hours. Ribs should be tender but not 'fall off the bone'.
Take the Dutch oven out of the oven and transfer ribs to a platter. Keep ribs warm. Strain liquid to remove vegetables, reserving the liquid. Remove as much fat as possible from the liquid.
Add liquid, remaining beef stock and remaining Irish Whiskey in a saucepan and bring to a boil. Boil until you reach the consistency you want. (Alternatively dissolve 2 tablespoon corn starch in some of the hot liquid and stir the slurry in to the pot to thicken the sauce).
Sample the sauce and adjust the salt and pepper to taste.
Pour sauce back over ribs and serve over mashed potatoes or pasta.