Heat the oil over medium heat in a small saucepan. Add the shallots and saute until golden, about 3 mins.
Preheat the oven to 350 degrees. Lay the sliced bread in an even layer on a sheet tray.
Heat the olive oil in a small saucepan over medium heat. Add the mustard seeds and cover immediately. Careful! The seeds will begin to pop immediately. Shake the pan a few times as they cook, and carefully check after a minute or two if they're browned. Remove from the heat and sprinkle with salt. Leave covered until they finish popping. Pour the seeds on a papertowel lined plate to drain.
Spread the brie onto the crostini. Add a dab of cranberry chutney and a sprinkle of the fried mustard seeds.