Preheat the oven to 200°C.
Drizzle soda farl with oil, season, and grill on a hot pan for two minutes per side.
Simmer milk, sliced onion, bay leaf, and thyme in a shallow pan to infuse.
Poach the kipper in the milk for five minutes and set aside in a warm place.
Melt butter in a frying pan and soften chopped onion and garlic for two minutes.
Stir in mustard and vinegar and cook for an additional two minutes.
Pour in cream and simmer for five minutes until the sauce reduces and thickens.
Poach the egg in a whirlpool of simmering water and vinegar for three minutes.
Serve by placing egg and kipper on the farl slices and topping with sauce.