Combine the brown sugar, soy sauce, red onion, jalepeno, ginger, rice vinegar, and sesame seeds in a bowl and whisk until smooth. (Optional step) Sprinkle pork with salt and pepper and brown in a large pan set over medium high heat. Brown all or most sides, about 3-4 minutes per side. Place pork in a slow cooker. Pour soy sauce mixture over the top. Add the garlic cloves. Cover with lid and cook on low for 7 hours, on high for 4 hours. Shred pork slightly into large pieces and continue to cook uncovered for an additional 30 minutes. Shred pork completely and use immediately or store in the fridge for up to 1 week in the freezer for up to 3 months.