In a mixing glass, add the cognac, demerara syrup, orange bitters, and Angostura bitters. Fill the glass with ice and stir until well chilled, about 30 seconds.
Strain the mixture into a pre-chilled rocks glass filled with fresh ice. Preferably, use one large ice cube.
Express a lemon peel over the drink to release its essential oils and then add the peel as garnish.
If you do not have demerara syrup on hand, you can make it by combining equal parts demerara sugar and water in a small saucepan. Heat over medium-low heat, stirring gently until the sugar dissolves. Do not let the mixture boil. Remove from heat, let cool before using.