Melt the butter, stir in the tea, simmer on a mild heat for 3 minutes, then let it steep for 30 minutes. Put the tea butter through a sieve in a bowl, squeeze out well. Mix together with the sugar until very frothy. Stir in the eggs one at a time. Mix the flour with the starch and baking powder and gradually stir into the butter mixture alternately with the buttermilk. Let the dough rest for about 20 minutes.
Whip the cream until stiff, stir the rum into the plum jam and fold it very gently into the whipped cream.
Bake the waffles in portions and serve with the plum cream.