Prepare your pie crust. If you follow my recipe, it will have to rest in the fridge for about an hour ahead of time. If you chose a store bought pie crust, you just saved some time!
Place the berries in a large bowl. If you thawed your berries, give them a little once over with a paper towel to dry them off a little.
Add in the lemon juice.
In a small bowl, add in the sugar and cornstarch. Stir until combined. Pour into the bowl of fruit and carefully stir until all of the fruit is covered. Set aside.
Preheat oven to 400 degrees.
Lightly flour a clean counter top. Roll out into a circle. You'll want it to be about 12 inches. You can eyeball your pie plate and the circle to see if you're close. That's what I do.
Once your circle is right, fold the dough in half and pick it up and place onto the pie plate. Unfold the dough and push the dough onto the bottom and sides.
Trim the edges. I cut them even with the edge of the pie plate using a knife.
Go ahead and put the pie filling into the bottom of the crust.
Slice the butter into thin slabs. Place them on top of the pie filling.
To make the lattice crust, roll the dough out like we did with the bottom crust. Once roll out to about 12 inches in diameter, use a pizza cutter or pastry cutter and cut inch strips. Place the strips over and under each other kind of like a basket weave.
With your forefinger and thumb, crimp the pie crust together. I usually form a "U" with my forefinger and thumb on the inside of the edge. With my other forefinger, I push the dough between my thumb and forefinger resting on the inside. (I hope this helps)
Crack the egg in a small bowl. Using a pastry brush, brush the egg wash on the top of the pie.
Place the pie in the oven for 20 minutes. Lower the temperature to 375 degrees and let the pie bake for another 50 minutes. The juice will bubble up on the top of the pie crust. Let the pie cool. Cut and serve.