Preheat oven to 375°F. In a large bowl, combine flours, honey, baking powder, baking soda and ¼ tsp salt. Add safflower oil, stirring until mixture resembles coarse crumbs. Add buttermilk and stir until just moistened. Transfer to a lightly floured surface and knead with your hands 5 times. Press dough with your hands or a rolling pin into ½-inch thickness. With a biscuit cutter (or the rim of a round glass dipped in flour), cut into 4 3-inch biscuits and transfer to a large parchment-lined baking sheet, leaving 1 inch between each. Bake for 10 to 12 minutes, until tops are lightly browned.
Meanwhile, in a large skillet, heat olive oil on medium-high. Add chicken and cook, stirring frequently, for 3 minutes, until golden brown. Add mushrooms and garlic and cook, stirring occasionally, for 3 to 5 minutes, until mushrooms soften and release liquid and chicken is cooked through. Add sage and stir to coat. Cook, stirring frequently, for 1 minute, until sage is fragrant. Remove from heat and stir in sour cream, parsley, pepper and additional salt. Slice biscuits in half through the middle and layer spinach and mushroom mixture between halves, dividing evenly.