Rinse tangerines with hot water, dab dry. Cut with peel into very thin slices. Sprinkle with 500 g sugar. Leave to soak for one night
Rinse strawberries, clean, chop, bring to boil with jelling powder while stirring. Add remaining sugar and tangerine slices along with juice that has run out. Heat again and make bubbling for 5 min while stirring.
Fill the jam into prepared jars, seal on the spot.