Line an 8 x 8-inch square baking tin with parchment, allowing a 1-inch overhang on all sides. Spray with nonstick spray.

In a small saucepan, warm whipping cream and rosemary sprigs. Remove from heat and infuse for 20 minutes. Remove the rosemary.

Gently rewarm cream. Add butter and fine sea salt and stir until the butter melts.

In a separate medium saucepan, combine granulated sugar, corn syrup, and water. Cook, without stirring, until mixture resembles honey, and temperature reaches 365° F / 185° C on a candy thermometer. Swirl the pan occasionally to keep the caramel moving.

Remove from heat. Pour the warm cream into the sugar syrup, then wait a minute for the bubbles to subside.

Return to heat. Cook until temperature reaches 250° F / 120° C on a candy thermometer, or slightly higher for firmer caramels.

Remove from heat. Stir in the pure food grade rosemary oil.

Immediately pour into prepared tin. Sprinkle with coarse sea salt or flaky sea salt.

Allow to sit, uncovered, until caramel sets, about 6-8 hours, or overnight.

Lifting by the parchment edges, remove the caramel slab and place on a large cutting board. Peel away the parchment. With a sharp, well-oiled chef’s knife, cut caramel  into squares or rectangles.

Wrap caramels in squares of parchment. Store in an airtight container at room temperature for up to 2 weeks.