Whisk flour, eggs, and milk into a smooth batter and season.
Pour batter into a jug and rest in the fridge, preferably overnight.
Preheat the oven to 220°C.
Heat a 12-hole muffin tin for five minutes, add beef dripping to each hole, and heat until smoking.
Whisk batter again, pour into tins, and bake for 10-15 minutes until golden.
Reduce red wine by half in a sauté pan, then add stock and reduce by half again.
Sauté sliced onions and thyme in butter for 12-15 minutes until soft.
Add brandy, flambé to remove alcohol, then stir in the reduced stock and boil.
Simmer the gravy for five minutes and adjust seasoning with salt and pepper.
Serve warm Yorkshire puddings topped with the onion gravy.