In a large skillet, melt butter over low heat.

Add chopped yellow onion and curry paste.

Cook, stirring occasionally, for about 5 minutes or until the onion is softened.

Transfer the onion mixture to the slow cooker.

Add cauliflower, diced potato, and broth to the slow cooker.

Cover and cook on low for 4 to 6 hours.

Once cooked, use a food processor or blender to puree the soup until smooth, working in batches if necessary.

Alternatively, use a hand mixer directly in the slow cooker.

Add the half and half (or milk), salt, and Tabasco sauce to the slow cooker.

Mix well.

Cover and continue cooking on high for an additional 10 minutes or until the soup is hot.

To serve, garnish each serving with thinly sliced red onion and chopped cilantro.