Make tofu dango: Add tofu and mochiko to a mixing bowl and use your hands to crumble the tofu into the flour. Keep mixing and pressing the mixture together to form a ball. Roll the ball around your bowl to pick up all the crumbs. Knead until it reaches the texture of an earlobe.
Shape dango: Pinch off 1-2 tbsp size of dough and roll into a ball. (I was able to make 10 balls.) Gently press down in the center with your index finger to make an indentation. (This helps the mochi cook more evenly.)
Cook dango: Bring a pot of water to a boil. Add dango (cook in batches if necessary, don't overcrowd the pot). The dango is cooked when it floats to the surface.
Cool dango: Place dango in ice water to cool and prevent further cooking.
Soup
For kirimochi: Toast in a toaster oven or regular oven at 450°F until puffed up and golden brown.
Make soup: Add anko, water, black sesame, and salt to a saucepan and bring to a boil. Adjust consistency as desired - add more water for a thinner soup, or boil for a few minutes to evaporate liquid for a thicker soup.
Combine: Place dango/mochi in serving bowls and pour hot soup over. Enjoy!
Notes
Anko: You can use store-bought or homemade tsubu-an (chunky red bean paste) or koshi-an (smooth red bean paste) as desired. I prefer chunks of red beans in mine. See how to make your own anko here.Black Sesame: You can omit the black sesame and just prepare regular zenzai, but I love the combination of black sesame and anko.