In a stock pot, combine the frozen blueberries with the sugar, corn starch, water, lemon juice, salt and cloves. Warm over medium low heat to thaw the blueberries, stirring occasionally.
Increase the heat to medium and bring to a boil, stirring frequently. Once it's close to boiling, stir constantly, then boil for 1 full minute while stirring.
Remove from the heat and stir in the vanilla and butter.
Let the filling cool to room temperature before filling and baking your pie.TIP: You can also make the filling 1 day in advance, and refrigerate until needed, taking it out of the fridge an hour before needed, to take the chill off.
Divide the dough in half, wrap each portion in plastic wrap, and refrigerate until needed.TIP: You can refrigerate the dough for up to 5 days, or freeze it for up to 3-6 months. Let it warm up to room temperature until you can roll it out without too much difficulty.
Assemble and Bake
Preheat the oven to 375 F. Position a rack in the lower third of the oven to bake your pie. Line a baking sheet with parchment paper.TIP: The position of the oven rack is important. Baking the pie in the lower third of the oven brings the bottom crust closer to the heating element so that it fully bakes through, without over-browning the top crust.
On a floured surface, roll out half the dough to between 1/4-1/8 inch thick, and fit it into a 9-inch pie pan or tart pan. Trim the edges, leaving about 1/2 inch overhang all around.
Pour the cooled blueberry filling into the crust, and set the pan in the refrigerator to stay cool while you roll and cut the lattice strips.
On a floured surface, roll out the second half of the dough to 1/8 inch thick, and cut into strips. Arrange the strips of dough in a lattice pattern over the blueberry filling. Press the dough together all around the edges, then trim the edges.
Lightly beat the egg with the milk, and brush the egg wash over the lattice crust. If you like, sprinkle with a little granulated sugar for a crunchy finish.
Set the pan on the baking sheet (to catch drips), and bake for about 45-60 minutes, until the filling is thick and bubbling over and the crust is golden brown and crisp.TIP: The type of pan you use (ceramic, glass or metal), the position of your oven rack, and the temperature of your ingredients will all affect how long it takes a pie to bake. The important thing to watch is the filling. If it's not bubbling, the pie is not done, and the filling won't set up correctly. Ceramic pie pans don't conduct heat as well, and pies might take anywhere from 60-90 minutes to bake through. A metal pan conducts heat much better, and when I baked this blueberry pie in my metal tart pan, it was done in less than 50 minutes.
Cool the pie completely (at least 5-6 hours, or overnight), so the pie filling can set up before you slice it.TIP: If you want to speed up the cooling process so the filling sets up faster, let the pie cool at room temperature for 1-2 hours, then put the pie in the freezer for another 1-2 hours. Do NOT put a piping hot glass or ceramic pan into your freezer, or it could crack.
Notes
Leftover blueberry pie should be stored at room temperature, covered loosely, and is best eaten within 2 days.