In a large bowl, dissolve Prague Powder in warm water.
Add salt, sugar, pickling spice, garlic, and paprika to mixture. Put brisket in a stone jar or pressure cooker, pour brine over and cover with a weighted-down plate. Cover jar or pressure cooker. Allow to stand in a cool place for 3 weeks or more, turning meat occasionally. Transfer meat to kettle or deep pot, add cold water to cover, bring to boil, and simmer meat for 1 hour. Drain kettle, add fresh cold water to cover; add bay leaves, cloves, and onions. Gradually bring water to boil, then simmer meat gently until tender.