In blender, add eggs, half-and-half, cream cheese, cornstarch, mustard, salt, pepper, thyme and pepper flakes. Cover and blend about 30 seconds or until smooth. Add to slow cooker; stir to combine. Cover; cook on High heat setting 2 hours 30 minutes to 3 hours 30 minutes or until temperature reaches at least 160°F in center and egg mixture is set. Remove slow-cooker ceramic insert from heat. Sprinkle remaining 1/2 cup Gruyère cheese over casserole; cover, and let stand 15 minutes.