Firstly, to make the butterscotch sauce (makes 330ml/1 1/3 cup):
160 ml (2/3 cup) thin cream
155g (3/4 cup firmly packed) brown sugar
50g (2 1/2 tbs) butter
2 tsp vanilla essence
1. Place all ingredients into a heavy-based saucepan, stir over medium heat for 5 minutes or until well combined.
2. Increase heat to high and bring to the boil. Reduce heat to low and simmer, uncovered, stirring often, for 5 minutes or until the sauce thickens. This can either be set aside at room temperature for use later or can be used straight away to...
Secondly, make the butterbeer (makes 2 small serves):
1 cup soda water
1/2 cup butterscotch sauce
1/2 tbs butter
1. Measure butterscotch sauce and butter into a microwave safe measuring jug. Microwave on high for 1-1.5 minutes, or until the syrup is bubbly and the butter is completely incorporated.
2. Stir and cool for 30 seconds, then slowly mix in soda. Mixture will fizz quite a bit.
3. Serve in coffee mugs or glasses while warm.