Combine the berries, sweetener, and water in a medium saucepan over medium heat.
Bring to a simmer and cook, stirring frequently, until the berries can be easily mashed with a fork. Stir in the glucomannan and set aside.
Bars
Preheat the oven to 325ºF and line an 8x8 inch metal baking pan with parchment paper.
In a microwave-safe bowl, melt the peanut butter and butter together, stirring until smooth.
In a large bowl, whisk together the almond flour, sweetener, collagen powder, baking powder, and salt. Stir in the melted peanut butter mixture, the egg, and vanilla extract until well combined.
Press two thirds of the dough into the bottom of the prepared pan. Spread the raspberry filling mixture evenly over the crust.
Take the remaining dough and crumble it over the filling. Bake 25 to 35 minutes, until the top is lightly browned.
Remove and let cool completely, then lift out of the pan by the edges of the parchment. Cut into squares.
Notes
Storage Information: You can store the bars in an airtight container at room temperature for up to 3 days. They will last for up to a week if you store them in the refrigerator. Wrap individual bars in foil or plastic wrap and freeze the bars for up to 3 months