Grind freeze-dried strawberries:

Note: You'll need 2 (1-ounce) bags of freeze-dried strawberries. Grind 1½ bags together into a fine powder using a blender, spice grinder, or food processor. Reserve the remaining ½ bag, unblended, to garnish the tops.

Cook tangzhong paste:

In a small saucepan, whisk together the water and bread flour. Cook over medium heat, whisking constantly, until the mixture thickens to a paste, about 4-5 minutes. Scrape into a small bowl and set aside until ready to use.

Mix dough ingredients:

In a stand mixer fitted with the dough hook, combine the bread flour, sugar, yeast, and salt. Add the milk, egg, and tangzhong; knead on low for 2 minutes until a dough forms.

Add strawberry powder:

Add the freeze-dried strawberry powder and knead until evenly incorporated and pale pink.

Knead in butter:

Knead in the butter 1 tablespoon at a time, mixing until fully incorporated. Increase speed to 2 and knead for 12 minutes, until smooth, elastic, and the dough passes the windowpane test. The dough should feel soft and tacky.

Rest dough:

Shape the dough into a ball, return to the bowl, cover, and rest for 30 minutes.

Cut parchment squares:

While resting, cut 9 parchment squares, 4-5 inches each.

Roll and cut donuts:

Roll the dough on a lightly floured surface to about 3/4-inch thick. Cut out donuts, rerolling scraps twice to get as many donuts as possible.

Proof donuts:

Place each donut on a parchment square and arrange them on a baking tray. Cover loosely, and let rise until puffy and doubled, 60-75 minutes. If your kitchen is cold, this could take longer. Meanwhile, read through the next steps below.

Heat oil:

When donuts are halfway proofed, heat 3-4 inches of oil in a heavy-bottomed pot over medium-low heat to about 340°F (170°C). Keep the oil between 330-350°F (165-177°C) while frying. Oil that's too hot can over-brown the donuts, while oil that drops too low during frying can make them greasy. Adjust the heat as needed to maintain a steady temperature.

Prepare cooling rack:

Set a wire rack over a baking sheet and set aside.

Check donut readiness:

The donuts are ready when they feel light and airy and slowly spring back when gently pressed.

Fry donuts:

Working in batches of 2, lower donuts into the oil with the parchment attached. Remove parchment after 5-10 seconds. Fry for 2½ minutes total, flipping halfway, until golden brown with a pale ring around the center.

Cool donuts:

Transfer to the wire rack and cool completely.

Coat in strawberry sugar:

In a medium bowl, combine the sugar and strawberry powder. Once cooled, roll just the sides of the donuts in the sugar.

Make strawberry glaze:

In a large bowl, whisk together the powdered sugar, strawberry powder, and water until smooth. The glaze should be thick, but thin enough to flow smoothly when piped or spooned onto the donuts.

Glaze and garnish:

Spoon the glaze over the tops. Garnish with sprinkles or more freeze-dried strawberries and enjoy!