A few things to know before you begin. Go with whatever apple you like, except for Red Delicious which I’d never use for pie, personally. I don’t think you can go too wrong, and there’s something about the readily available Granny smith that works well here. The cardamom seems such a small amount, and your hunch might be that the flavor is barely perceptible. It all depends on the sensitivity of your palate. My girls pick up flavors, be them ever so faint, so I went light-handed here. If you love cardamom, and want it to be more prominent, go for ¼ teaspoon, but I probably wouldn’t suggest more than that. And a note about cutting the vents into the top. This should always be done after brushing with the egg wash, otherwise your vents will close up. I thought this was worth mentioning, so if you already know that, kudos, and if you didn’t, then it’s a good tip to remember.
Combine the apples, strawberries, sugar, flour, lemon juice, and cardamom in a deep bowl. Give it a stir to mix well, then set aside so the fruit can release its juices.
Meanwhile, lightly flour a counter or cutting board. Roll one of the pie crusts into a 10-inch (25-cm) circle. Fit it into a 9-inch (22-cm) pie plate, letting the crust hang over the sides—don’t trim it just yet.
Roll out the second pie crust into a 9-inch (22-cm) circle.
Stir the filling, and spoon it into the pie plate. Cover with the remaining rolled out pie crust. Use a scissor to trim the edges, and flute them, or crimp closed with the tip of a fork. Brush the top with the egg wash. Use the tip of a sharp paring knife to slit vents in the top (or a small round cookie cutter works, too).
Bake for 15 minutes, then reduce oven temperature to 350º (180ºC). Bake for 35 to 40 minutes more, until the crust is golden, and juices begin to bubble from the pie.