Generously grease the sides and bottom of a 7 inch springform pan with butter. Then, in a large bowl, toss peaches, with brown sugar, lemon juice, cinnamon and cornstarch. Add to the pan.
Next mix flour, brown sugar, white sugar, baking powder, cinnamon and salt in another large bowl. Add in bits of chilled butter, kneading to combine. Pour in boiling water, mix, then dollop on top of peach mixture in the springform pan. Cover the pan tightly with aluminum foil.
Pour 1 cup of water into an 8-quart Instant Pot then add trivet. You may need to fold the handles underneath. Gently balance the covered springform pan overtop of trivet.
Place lid on Instant Pot and make sure valve is set to seal. Press the pressure cook button and set to high, then pressure cook for 25 minutes.
The Instant Pot will take about 5-10 minutes to come to pressure, then notify you it's done by beeping. Press the Cancel button then do a quick release of the pressure on the Instant Pot by flicking the switch at the top with a spoon. Open the lid when pressure gauge has dropped and the lid opens easily.
Let the peach cobbler cool with the lid off for at least 15-20 minutes. Meanwhile, preheat the oven using the broil setting. Use oven mitts to carefully remove the cake pan, then broil for 2-3 minutes, watching closely so it doesn't burn. Serve warm with ice cream or whipped cream and enjoy!