Preheat oven to 400°F and have a 10-inch cast iron skillet or any similar size baking pan ready.
Make topping
Add all topping ingredinets (except butter) into a medium bowl and mix to combine, making sure to break any lumps in brown sugar.
Add butter amd mix using your fingertips, until the butter is well distrubuted and the mixture is slightly clumpy.
Make filling
Peel the skin, remove the pits and slice each peach into 8 to 10 wedges. Tip: Use ripe yet firm fruits. They are easier to peel with a vegetable peeler.
Add them into the skillet along with the white sugar, cornstarch, vanilla extract and lime juice. Toss until combined and spread evenly. Tip: Avoid adding any remaining peach juices to prevent a watery filling.
Assemble and Bake
Sprinkle the topping, crumbling with fingers if required to get that crumbly topping.
Bake for 30 to 35 minutes or the topping is deep golden in color. Serve with vanilla ice cream.
Video
Notes
Skillet - I use a 10-inch oven-safe cast iron skillet. Use a 9x9 square or round baking dish instead. Filling - Do not leave the peaches sitting around coated in the sugar. Make ahead - Assemble crumble topping, cover, and set aside for a day. Chop peaches and store in an airtight container in the fridge. Toss peaches in cornflour, sugar and vanilla just before baking.