How to make apple chunks in apple pie stay intact?

The only trick I know of is to use a different variety of apple-- some will turn to complete mush, while others stay firm. Unfortunately, unlike potatoes, they don't tend to be marked at the super market as to which variety they are.

Now, I'm not familiar with Bramley, but from what I've found, it's compared to Granny Smith, which tends to hold up well in pies.

I'd recommend blind baking your crust, if you aren't already, so the filling isn't in there as long, and possibly going with a thicker slice of apple when you're cooking, in hopes they won't break down as quickly.

update : in checking CookWise, there's a comment in the apple pie recipe that "briefly sautéing and poaching apples softens them slighly before the sugar, which prevents cells falling apart and preserves texture, is added"

Just recalled a pie I made a few years back that may help you out...

It was the end of the season, and I didn't have enough fresh apples left for both a pie and sauce. The pork roast in the oven cried out for sauce, but the ice cream in the freezer pleaded for pie... So I cooked up the sauce, and rolled out the dough, lining the bottom of the pie with dried apple slices, covering them with sauce and a solid top crust. The dried apples softened as they cooked, and by the time the crust was done I had a thick, intensely-flavored filling.

So if you have apples to spare, slice and dry a few, then mix those into your next pie.

The first technique that comes to mind would be to bake the crust "blind" first. That is, you put it in the oven with a weight on it (so that it doesn't bubble up). Once the crust is mostly baked, add the filling and put in the oven for a second session. That way, the filling doesn't need to wait for the crust to be done.

In all honesty, I actually like the apples mushy in my pie. However, that's a matter of personal taste.

My understanding is that this is mostly to do with the apple variety. Here is a chart of which apples will behave well in pie. I see from Wikipedia that Bramley's are considered a definitive baking apple. Is it possible that your tree isn't really Bramley's?

I usually pre-cook the apples in a saucepan, and then assemble the pie. Then I can cook the crust at ridiculously high temperatures to do the crust in about 10-15 minutes, which doesn't allow enough time for the apples to continue cooking.

See What is the enzyme that makes apples's pectin heat resistant? And can it be added to other fruits to achieve similar results? ... pre-baking the apple pieces separately for a couple ten minutes at ~60°C can indeed make them hold up better in fillings.

Try mixing your apples with the sugar and letting them drain in a colander over a bowl for 15-20 minutes. Put the juices in a pan over low heat and reduce by at least half. Assemble your pie and pour the reduction over the apples.

And check your oven's temperature with a good oven thermometer. You may be cooking the pie too long if it's under temperature.