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. With kitchen tongs, remove the rosemary.

Rewarm cream over low heat. Add butter and fine sea salt, stirring until the butter melts.

In a separate medium saucepan, combine granulated sugar, corn syrup, and water. Cook, without stirring, until mixture resembles honey, about 15 minutes, or 290° F (143° C) on a candy thermometer. Swirl the pan occasionally to keep the caramel moving.

Remove from heat. Pour warm cream over caramel, then wait a few seconds for the bubbles to subside.

Cook over medium heat until temperature reaches 255-260° F (124°-127° C) on a candy thermometer.*

Remove from heat. Swirl in the 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.