Gently melt the butter and heavy cream together in a small saucepan over medium heat. Once melted, set it aside to keep warm.
In a separate medium saucepan, combine the allulose, water, sea salt, molasses, and vanilla extract. Stir everything until well mixed.
Heat this mixture over medium-low heat, stirring occasionally, until it reaches at least 350°F (use a candy thermometer for best results) and you notice a slight change in color.
Carefully pour the warm butter and cream mixture into the allulose mixture you just heated. Don't worry if it bubbles up; just keep stirring gently until it settles down.
Continue cooking the entire mixture over medium-high heat, stirring constantly, until it deepens into a rich, amber caramel color.
To check if your caramel has reached the perfect chewiness, drop a small amount onto a spoon and dip it into ice water. Once cooled, test its consistency.
When it's just right, pour the caramel into a pan that's been lined with buttered parchment paper.
Let the caramel cool completely at room temperature until it's firm before cutting it into delicious, chewy candies.