1. Place beans in a large bowl, and cover with water 2 inches above beans. Cover and chill 8 hours; drain.
2. Cut sausage in half lengthwise; cut each piece in half crosswise. Grate cut sides of sausage using the large holes of a box grater into a bowl, discarding casing. Sauté grated sausage in hot oil in a 6-qt. pressure cooker over medium heat 2 to 3 minutes or until just browned. Add garlic, next 2 ingredients, and, if desired, red pepper, and sauté 1 minute or until fragrant. Add onion mixture and ham base, and sauté 3 to 4 minutes or until vegetables are tender. Stir in beans and 3 cups water. (Do not fill pressure cooker more than two-thirds full.)
3. Bring to a boil over medium heat, stirring occasionally. Cover pressure cooker with lid, and lock. Cook until pressure indicator reaches HIGH pressure (15 psi). Maintain pressure, reducing heat as needed, and cook 20 minutes. Remove from heat, and let stand until indicator shows no pressure. Once pressure is fully released, unlock and remove lid. Gently mash some of the beans, if desired. Stir in hot sauce; add salt to taste.