Prepare apple filling: In a skillet over medium‑high heat, melt butter with brown sugar, cinnamon, and ginger. Add chopped apples and cook 5–7 minutes, stirring until softened and syrupy. Remove from heat, stir in almond flour, and cool completely.

Make psyllium gel: Combine psyllium husk with lukewarm water. Mix well until it forms a thick gel (about 40 seconds).

Combine dry ingredients: In a large bowl or stand mixer, whisk tapioca starch, millet flour, sorghum flour, sugar, yeast, baking powder, xanthan gum, and salt.

Mix wet ingredients: Stir milk, egg, and oil into the psyllium gel until incorporated. Add this mixture to dry ingredients.

Knead dough: Mix on medium speed 4–5 minutes (or 6–8 minutes by hand) until dough is smooth and elastic. It will be sticky. Lightly flour hands and chill dough 30 minutes for easier rolling.

Shape buns: Roll dough into a 9×16‑inch rectangle. Brush surface with whisked egg and spread apple filling evenly. Cut into six 16‑inch strips, roll tightly into logs, and tuck ends under.

Proof: Place rolls on parchment‑lined baking sheet, spaced apart. Cover and proof until doubled in size, about 1 hour 15–30 minutes.

Prepare crumble: Combine flour blend, brown sugar, xanthan gum, and salt. Rub in cold butter with fingertips until crumbly and clumpy.

Bake: Preheat oven to 375°F (190°C). Top proofed rolls generously with crumble and bake 18–20 minutes until golden brown.

Cool & serve: Let buns cool before serving. Enjoy warm or at room temperature.