Not just sandwiches, drinks too in Banh Mi 75 Banh Mi Recipes for Authentic & Delicious Vietnamese Sandwiches (Adams Media, July 2013) by Phamfatale Jacqueline Pham. 

Thai Basil Seed Drink

Nước Hột É

Yields 12 servings

This odd-looking drink is, despite its appearance, very refreshing. Once soaked in warm water,
the seeds form a kind of gooey-textured shell. In addition to the Thai basil seeds, soaked malva nut
tree seeds are usually included in this unusual drink.

¹⁄³ (2-ounce) package dried malva nut tree seeds (đười ươi)
¼ cup Thai basil seeds
2 quarts water
½ cup superfine sugar, to taste
4 tablespoons honey
3 cups ice cubes, or more
2 limes, freshly squeezed

1. Preparing the malva nut tree seeds: Cover the malva nut seeds completely in warm water and soak for 30 minutes. Separate the cotton-like texture from the skin and seeds, discard the skin, and rinse the cotton-like texture in cold water. Squeeze out as much liquid as possible using paper towels. Set the seeds aside.

2. Preparing the Thai basil seeds: Place the basil seeds in a large strainer and rinse them under running water. Place the rinsed seeds in a large heatproof pitcher.

3. Assembly time: In a saucepan, bring 2 cups of the water to a near boil. Pour into the pitcher. Let the basil seeds gain in volume, which will take about 5 minutes. In the same saucepan, dissolve the superfine sugar with 1 cup of the water. Bring to a near boil, then add the honey. Pour the resulting
syrup into the pitcher. Add the remaining 5 cups of cold water and complete with lots of ice cubes. Add the lime juice and the malva nut tree seeds. Stir well. Adjust sweetness if necessary.

(Excerpted from Banh Mi by Jacqueline Pham, Copyright © 2013 by F+W Media, Inc. Used by permission of the publisher. All rights reserved.)