1. Prepare all ingredients: Grate the cheddar and Gruyere cheese freshly (avoid pre-shredded for smoother melting). Finely chop onions and garlic. Have Oktoberfest beer at room temperature.

2. Make the roux: Melt butter in a medium saucepan over medium heat. Add flour and whisk constantly for 1-2 minutes until the mixture turns light golden and develops a nutty aroma. This ensures the flour cooks properly and prevents lumps.

3. Sauté aromatics: Add diced onions to the roux and cook for 2-3 minutes until softened. Add minced garlic and cook for another 30 seconds until fragrant.

4. Add cheese gradually: Reduce heat to low-medium. Add the shredded cheddar and Gruyere in small handfuls, stirring constantly until each addition melts completely before adding more. This prevents lumps and ensures smooth consistency.

5. Incorporate beer: Slowly pour in the Oktoberfest beer while stirring continuously. The mixture will thin initially, then thicken as you stir. Continue stirring for 2-3 minutes until smooth and creamy.

6. Add cream and seasonings: Stir in heavy cream or sour cream, garlic powder, smoked paprika, and cayenne pepper (if using). Season with salt and black pepper to taste. Simmer on low heat for 3-5 minutes, stirring occasionally.

7. Adjust consistency: If the dip is too thick, add more beer 1 tablespoon at a time. If too thin, simmer longer while stirring until desired consistency is reached.

8. Serve warm: Transfer to a warm serving bowl or pretzel-shaped dish. Garnish with chopped fresh parsley. Serve immediately with soft pretzels or pretzel bites.