Preheat and prep – Crank your oven to 400°F (200°C). Roll out your bottom crust into a 9-inch pie pan. Keep it snug and don’t stress the edges—they just need to hug the filling.

Mix the filling – In a bowl, toss blackberries with sugars, cornstarch, lemon juice, cinnamon, and salt. Mix gently; you want berries coated, not mashed.

Assemble the pie – Pour the filling into the bottom crust. Dot with butter. Carefully lay the top crust on, trimming excess dough and pinching edges to seal. Make tiny slits in the top to let steam escape—your pie will thank you.

Egg wash magic – Whisk the egg with water, brush it over the crust for that perfect golden sheen. Optional: sprinkle a pinch of sugar for sparkle.

Bake like a pro – Pop it in the oven for 20 minutes at 400°F (200°C), then lower to 350°F (175°C) and bake another 35–40 minutes. The filling should bubble and the crust should be golden brown.

Cool before attacking – Yes, it’s tempting, but let it cool 2–3 hours so the filling sets. Slice it, serve it, and brace yourself for compliments.