In a large mixing bowl, combine flour, rolled oats, pistachios, ginger, cinnamon, cardamom & sugar.
Using a pastry blender, combine flour mixture with butter until it resembles a coarse meal. Store the mixture in the fridge until ready to use.
Filling
Preheat oven to 375 F.
Place a large saucepan over medium heat & add in butter. Once the butter is melted, add in the (thawed) peaches, brown sugar, cinnamon, allspice, cardamom & black pepper. Bring the mixture to a simmer & cook for an additional 10 minutes.
Pour cooked peaches into a large casserole dish & evenly top with the pistachio-oat crumble.
Bake for 40 minutes, or until the top is golden-brown & the sauce bubbles around the edges.
Once finished baking, serve warm with ice cream or whipped cream if you wish.