yourfavouritepastry for top and bottom crust of a 9-inch pie dish(for a tender flaky gluten free crust, use 1½ times this recipe, chilled before rolling it out)
Top and tail the gooseberries (pinch off the little stem end and blossom end). Peel the apple, cut it into quarters, cut out the core, and cut each quarter in half to make 8 wedges, then cut each wedge into thin crosswise slices.
Toss the gooseberries, apple, sugar, tapioca, water, and vanilla in a bowl, then scrape it into the chilled bottom pie crust. Dot the top of the pie with bits of the butter.
Roll out the top crust, put it onto the pie and crimp the edges together with the bottom crust. Cut a few slits into the top of the pie to allow the steam to escape.
If using, brush the top of the pie with cream, milk, or diluted egg yolk, then sprinkle with the tablespoon of sugar. If using a shallow (regular) pie dish, set it onto a foil or parchment lined baking dish to catch any filling that might bubble over.
Bake at 450°F (230°C) for 10 minutes, then lower the heat to 350°F (180°C) and bake for an additional 35 to 40 minutes, until the pie is golden brown and the filling is bubbling up through some of the slits.
Allow the pie to cool fully, then cut it into 6 wedges. Serve with ice cream or whipped cream.
Notes
Gooseberries have an enzyme that prevents some starches from thickening - tapioca works the best here. If you don't have minute tapioca, use an equal weight of tapioca starch.The amount of sugar here makes a tart 'n' tangy pie. If you prefer a sweeter pie, increase the sugar to your liking.Gooseberries release a lot of juice when baking - the apple provides a bit of body to the filling without changing the flavour. If you don't have a Granny Smith apple, use any variety you have.*If you don't have gooseberries, sliced rhubarb makes a very good substitute.