Place the stir fry strips, chopped onion, diced peppers, can of tomatoes, curry paste, sugar, and cream in a large resealable bag.
Squish together to combine the ingredients.
Remove excess air, seal, and freeze.
On the day of cooking, thaw the bag.
Either stir fry the bag contents on high heat until the beef is cooked through or cook in the slow cooker for 4-6 hours on low.
You can serve the beef curry alongside or on top of rice, wrapped up in flour tortillas, or on its own. Garnish with fresh cilantro if desired.