1. Cut roasted, peeled chilies into thick slices; combine chili, water and whipping cream in a blender; blend until smooth.
2. Pour the mixture into a saucepan; heat to a boil; add the butter, salt and pepper.
3. Slowly stir in the polenta; turn the heat to low and cook, stirring, until the polenta grains have softened, about 3 minutes.
4. Serve with a dollop of the crema as a garnish.
5. Note: to roast chilies, hold with a fork over a gas flame to blacken skin on all sides; place in a paper bag or bowl covered with plastic wrap until cool; remove stem, skin and seeds.
6. You can also roast them over an outdoor grill.