Add <quantity>40<unit>ml</unit></quantity> of amaretto and <quantity>40<unit>ml</unit></quantity> of bourbon to a cocktail shaker

Add <quantity>30<unit>ml</unit></quantity> of fresh lime juice, <quantity>10<unit>ml</unit></quantity> of simple syrup and <quantity>1<unit>tsp</unit></quantity> of powdered egg white

Fill the cocktail shaker with ice cubes and shake vigorously until thoroughly chilled

Strain the cocktail and discard the ice cubes. Close the cocktail shaker and shake for 30s until smooth and velvety

Add <quantity>1</quantity> clear ice to a glass and strain the cocktail over it

Add <quantity>4<unit>dashes</unit></quantity> of angostura bitters

Express a lemon peel over the glass and rub it around it. The amaretto sour is ready

Cheers!