Ingredients

Fruit Mixture:

1 1/4 cups cubed rhubarb
1 1/4 cups cubed strawberries
2 Tbs white sugar

Dough:

2 cups all-purpose flour
2 1/2 tsp baking powder
1/2 tsp baking soda
1/2 tsp fine salt
1/2 cup (1 stick) frozen unsalted butter
1/4 cup white sugar
2 Tbs reserved fruit syrup
3/4 cup cold buttermilk

Egg Wash (optional):

1 large egg
2 tsp water
Lemon Icing Drizzle (optional):
1/3 cup packed powdered sugar
1 tsp finely grated lemon zest
2 tsp lemon juice, plus more as needed

Directions

Step 1
Cut ribs of rhubarb in half lengthwise and slice into 1/4-inch pieces; place into a bowl. Add cubed strawberries and 2 tablespoons sugar. Toss to combine, cover, and let fruit macerate in the refrigerator for 1 to 2 hours.

Step 2
Combine flour, baking powder, baking soda, and salt in a mixing bowl; whisk to combine.

Step 3
Drain fruit in a strainer set over a bowl. Reserve the syrupy juices that pass through.

Step 4
Grate frozen butter into the flour mixture, while stirring with a fork several times to coat butter pieces with flour. Add 1/4 cup sugar, and drained fruit, mixing with a fork until fruit is coated with flour.

Step 5
Add 2 tablespoons of the reserved fruit juices and pour in buttermilk. Mix with a fork just until the dry ingredients are incorporated into the dough. If the mixture is too dry to come together, add a little more buttermilk. If it seems too wet and sticky, add a little more flour.

Step 6
Preheat the oven to 450 degrees. Line a baking sheet with a silpat mat.

Step 7
Scoop or spoon equal portions of dough onto the prepared baking sheet. Whisk together egg and water in a small bowl. Brush biscuits with egg wash, and sprinkle with sugar.

Step 8
Bake in the preheated oven for about 25 minutes. Transfer to a wire rack and let cool completely.

Step 9
Mix powdered sugar, lemon zest, and lemon juice together in a small bowl for the lemon icing. Fill icing into a piping bag or a plastic bag with the tip cut off and drizzle icing over cooled biscuits.