Special equipment: 8 mini-loaf pans (2 by 3 1/2 inches) or a muffin tin, buttered and floured (unless your pans are nonstick
Combine both kinds of seeds and 1/2 cup of the tea in a bowl. Let soak to absorb and soften while you prepare the other ingredients. Heat the oven to 350 degrees F. Sift together the flour, baking soda, baking powder, and salt and set aside. Cream the butter until smooth in a mixer fitted with a whisk attachment (or using a hand mixer). Add the sugar and cream together until soft and fluffy. Add the eggs one at a time, mixing well after each addition. Add the vanilla and mix.
With the mixer running at low speed, add a third of the dry ingredients and mix. Then add half of the sour cream and mix. Add another third of the dry ingredients and mix. Add the remaining sour cream and mix. Add the remaining dry ingredients and mix until smooth. Add the seeds with their soaking liquid and mix until smooth. Pour into the pans and bake until firm in the center, 25 to 30 minutes. Let cool in the pans.
To make the glaze, whisk the remaining 1/4 cup of tea and the confectioners' sugar in a bowl until smooth. When the cakes have cooled, turn them out onto a work surface. Give the glaze a stir. Dip the bottom (the narrower side) of each cake lightly into the glaze until coated. Turn over so the glazed side becomes the top and set aside to harden.