Chill your glasses. Pop tall soda glasses or mason jars in the freezer for 10–15 minutes. Cold glasses help the foam hold longer and keep the drink frosty.

Soften the ice cream slightly. Let the carton sit at room temperature for 3–5 minutes. Slightly softened ice cream blends more smoothly with the soda and builds a lush foam.

Combine the sodas. In a measuring cup, mix equal parts root beer and cream soda. This gives you control over pouring and reduces overflow. If you prefer stronger spice, use more root beer; for more vanilla sweetness, favor cream soda.

Add the first scoop. Place one scoop of ice cream in the chilled glass. This anchors the foam and prevents everything from erupting as you pour.

Pour slowly along the side. Tilt the glass slightly and pour the soda blend in a slow stream along the inside wall. This creates a creamy head without runaway bubbles.

Add the second and third scoops. Gently slide in more scoops, one at a time. Top off with a little more soda if needed. Aim for a crown of foam that sits just above the rim.

Finish with flair. Add whipped cream, a cherry, and a light caramel drizzle if you like. A couple of drops of vanilla extract can round out the aroma.

Serve immediately. Include a long spoon and a straw. Take a spoonful of ice cream, then a sip of soda for the classic float rhythm.