Prick each sausage a couple of times with a fork then place on a baking tray.
Place baking tray into a preheated oven at 400.
While sausages are cooking heat skillet on high heat then add mustard seeds.
Toast mustard seeds shaking them around the skillet regularly and as soon as seeds begin to pop add tomatoes and scallions and saute for 1 minute.
Add salt and balsamic vinegar and continue to saute until tomatoes are warmed through and a little juice releases.
Place cover on skillet then remove from heat and set aside.
Check on sausages regularly, and turn as they brown.
Remove sausages from oven once cooked and tent with foil to keep them warm.
Fill a saucepan with water to two thirds and then add white vinegar
Heat on high until water is rumbling.
Lower heat and allow rumbling to stop and then carefully drop two eggs (one at a time) into the water.
With a slotted spoon, carefully swirl the water around the eggs. It will keep the eggs in tact.
Remove eggs once cooked to desired temperature with a slotted spoon and repeat until all eggs are cooked.
Warm croissants in oven for a few minutes then slice them in half.
Finally slice sausages and serve immediately.
To serve: place two halves of a croissant on a plate, then lay one sliced sausage on top of each croissant half.
Place an egg on top then add a dollop of tomato mustard seed relish.
Finish with a drizzle of olive oil.