SOAK mustard seeds in 3 cups of water for 1 hr. Drain and combine with 4 cups more water in a medium saucepan. Boil, stirring occasionally, until seeds are almost tender, 25 to 30 min. Strain. Rinse under cold running water. Strain again.
COMBINE mustard seeds, vinegar, sugar, water and salt in same saucepan.
Bring to a boil and stir until sugar dissolves. Reduce heat to medium-low and simmer for 10 min. Remove from heat and stir in turmeric. 3. Let cool and refrigerate for up to 3 months. Serve with tourtière.