The baker and pie coach Kate McDermott has many tricks to figure out when a pie is done, but her favorite is what she calls “the heartbeat of the pie.” She listens for a sizzle that tells her that the fat in the crust is cooking the flour, and for a thumping sound that indicates that the simmering liquid is bumping up against the top crust. Also, watch for bubbling: This will tell you that the temperature is high enough that the thickeners have dissolved into the filling. All-berry pies can…
