Substitutes:

• Ruby Port: I've once tried Tawny Port in place of Ruby. It gives a slightly different taste, nuttier and less fruity, but still very pleasing. If you're aiming for something lighter, a White Port can also work, but expect a change in flavor profile.
• Brandy: Cognac, being a type of brandy, makes for a direct substitute. When in a pinch, I've used a dark rum, which gives a slightly sweeter and more molasses-forward touch.
• Egg Yolk: For a vegan version, check out point d below.

Making a Pitcher of Porto Flip:

• Scale: For a pitcher serving 8, you'd want 12 oz of Ruby Port, 4 oz of Brandy, and 8 egg yolks.
• Mix: In a large pitcher, combine your ingredients. Make sure to whisk well to ensure the egg yolk is smoothly integrated.
• Serve: Pour the mixture into chilled Sour glasses, add the garnish, and serve immediately.

Making it Non-Alcoholic:

• Ruby Port Substitute: Go for a non-alcoholic red grape juice, and maybe add a hint of berry juice for depth.
• Brandy Substitute: Use apple juice or a non-alcoholic apple cider. It won't be the same, but it brings a pleasant fruitiness.
• Mix and Serve: Replace the original ingredients with these non-alcoholic alternatives and follow the instructions.

Making it Vegan:

• Egg Yolk Substitute: Aquafaba, the liquid from a can of chickpeas, is a miracle worker here. Use about 1 oz (30 ml) of aquafaba as a direct substitute for egg yolk. It'll give you that frothy texture without the egg.
• Prepare As Instructed: After substituting with aquafaba, follow the main instructions for a vegan version.