Line a large baking sheet with parchment paper or a silicone mat.
In a medium heavy-bottomed saucepan, combine the allulose sweetener, water, and grass-fed butter over medium heat.
Bring the mixture to a boil, stirring occasionally until the butter is melted and the sweetener is dissolved.
Use a candy thermometer to monitor the temperature, heating the mixture until it reaches 300 degrees Fahrenheit for the hard crack stage.
Once the temperature is reached, immediately remove the pan from the heat and stir in the slivered almonds, dried culinary lavender, dried thyme, and sea salt.
Quickly whisk in the collagen peptides until fully incorporated and smooth, working fast before the mixture begins to set.
Pour the mixture onto the prepared baking sheet and spread it into a thin, even layer using a heat-resistant spatula.
Allow the brittle to cool completely at room temperature for at least 30 minutes until it is firm and glass-like.
Break the hardened herbal candy into bite-sized shards and store in an airtight container.