01 -
Set your oven to 400°F and let it preheat.
02 -
Toss rhubarb together with sugar and pour in just a bit of water to avoid sticking. Cook it on medium-high until it starts boiling, then lower the heat. Stir and let it cook for around 4-5 minutes so the rhubarb softens slightly.
03 -
In a small cup, stir 1/4 cup water with the corn starch. Scoop some hot rhubarb liquid and mix it into the corn starch blend. Add that back into your rhubarb pot, stir, and cook until bubbling up. Continue cooking another 1-2 minutes before turning off the heat.
04 -
Combine flour, baking powder, and 1/3 cup sugar in a medium-sized bowl.
05 -
Slice the cold butter into the flour mixture until it becomes crumbly. Whisk the egg with the buttermilk in a new bowl, then gently stir it into the crumbly flour mixture. Stop mixing once a dough comes together.
06 -
Pour the rhubarb filling into a baking dish that holds about 1.5 quarts. Scoop out six pieces of biscuit dough and place them on top. Sprinkle the last tablespoon of sugar over the dough. Bake for 20-25 minutes, or until the fruit is bubbling and the biscuits turn golden.