Place onion over the base of a slow cooker and top with beef. Pour over combined jar of Five Tastes Curry Paste and coconut milk ensuring the whole piece of beef has been covered. Cover and cook on low for 6 hours.
Remove beef from slow cooker, pull or shred using two forks and set aside. Transfer meat juices to a small saucepan and simmer over medium-high heat for 5-10 minutes or until reduced by half. Season to taste. Combine meat and juices together until well combined. Cover loosely and refrigerate for 30 minutes.
Using a 10cm cutter, cut 18 rounds from pastry to line a 1/3 cup capacity muffin tray and fill each with beef mixture. Using remaining pastry, make tops by cutting 18 x 8cm rounds. Seal edges with a fork and egg glaze. Bake in a preheated oven at 200°C for 20 minutes or until pastry is golden brown.
Meanwhile, to make sliders, slice mini brioche buns in half. Place a little of the beef mixture on top of the base, sprinkle over some chopped peanuts and coriander. Top with pickled red onion and bun top and serve immediately with pies.