Warm 1 cup of heavy cream in a saucepan until bubbles form along the edges. Whisk in brown sugar until melted and no grains remain. Add whole rosemary sprigs. Reduce heat to low and simmer for 5 minutes. Remove from heat.

Whisk in remaining 1/2 cup of heavy cream and milk. Whisk in 2 egg yolks. Add sea salt and vanilla extract and whisk to combine. Cover and chill in the fridge. Allow to steep for at least 30 minutes, or overnight for a much stronger rosemary flavour. Remove rosemary sprigs and whisk mixture. Churn in ice cream maker according to manufacturer’s directions.

Place in freezer safe container and freeze for a minimum of 4 hours to allow your ice cream to harden.

Combine milk, 1 cup cream and rosemary sprigs in a saucepan over medium-low heat. Stirring occasionally, heat until bubbles start to form around the edges.

While the cream mixture is heating, whisk the egg yolks together with the remaining 1/2 cup cream until smooth in a heatproof bowl.

Temper the egg yolks by very slowly pouring half the hot cream mixture into the eggs while whisking constantly. Pour this mixture back into the saucepan.

Whisk in the sugar.

Continue cooking the mixture on low heat, stirring frequently, until it reaches a temperature of 185°F. If you don't have a food thermometer, the mixture is ready when it has thickened enough to coat the back of a spoon. Never allow the mixture to boil.

Cover and chill in the fridge. Allow to steep for 30 minutes, or up to overnight for a stronger flavour.

Remove rosemary sprigs.

Prepare your ice cream maker. Just before churning, add sea salt and vanilla extract and whisk to combine. Churn in ice cream maker according to manufacturer’s directions.

Place in a freezer safe container and freeze for a minimum of 4 hours to allow your ice cream to harden.