Oven & Skillet Prep : Position a rack in the center of your oven and preheat to 375°F (190°C). Place your 9-inch cast-iron skillet on the counter to use as your single mixing vessel.
Mix Biscuit Base : Directly into the cool skillet, add the almond flour, golden monk fruit sweetener, coconut flour, baking powder, cardamom, and salt. Whisk briefly to combine and break up any clumps.
Form the Dough : Create a shallow well in the center of the flour mixture. Pour in the melted butter, egg white, heavy cream, and vanilla extract. Use a fork to stir the wet and dry ingredients together until a shaggy, cohesive dough forms.
Isolate the Topping : Using your hands, gather the dough into a rustic ball and transfer it to a small plate or a piece of parchment paper. Set it aside for a moment. A few crumbs left in the skillet are perfectly fine.
Create the Berry Filling : Without wiping the skillet, add the fresh strawberries, raspberries, and blackberries. In a tiny bowl (or just sprinkled carefully), combine the granular sweetener and xanthan gum, then sprinkle this mixture evenly over the berries. Gently toss everything together until the berries are lightly coated. Arrange them in an even layer.
Assemble the Cobbler : Break the reserved biscuit dough into small, walnut-sized chunks. Scatter these pieces evenly over the surface of the berry filling. Don't press them down; let them rest on top.
Bake to Golden : Transfer the skillet to the preheated oven. Bake for 22–25 minutes. The cobbler is ready when the berry filling is bubbling thickly at the edges and the biscuit topping is firm and a deep golden-brown.
Rest and Serve : Carefully remove the hot skillet from the oven and place it on a heat-proof surface or wire rack. Allow the cobbler to rest for at least 10 minutes; this helps the filling set. Serve warm, perhaps with a scoop of low-carb vanilla ice cream.
