Preheat your oven to 350°F (175°C). Grease a 9x5 inch loaf pan and line it with parchment paper, leaving an overhang on the long sides.
In a medium bowl, whisk together the gluten free baking flour, almond flour, instant espresso powder, baking powder, baking soda, and salt. Make sure the espresso powder is evenly distributed with no clumps.
In a large bowl, whisk the melted butter with the dark brown sugar and granulated sugar until smooth and glossy. Add the eggs one at a time, whisking well after each. Stir in the vanilla extract and sour cream.
Fold the dry ingredients into the wet ingredients with a spatula until just combined. Fold in 1/2 cup of the toffee bits and all of the chocolate chips.
Pour the batter into the prepared pan and smooth the top. Scatter the remaining 1/4 cup toffee bits over the surface and sprinkle with turbinado sugar for a crackly cookie-like crust.
Bake for 52 to 62 minutes, until the top is set and a toothpick inserted in the center comes out with just a few moist crumbs. Tent with foil after 40 minutes if the top is browning too quickly.
Let the bread cool in the pan for 15 minutes, then carefully lift out using the parchment paper and cool on a wire rack. Slice when still slightly warm for melty toffee and chocolate pockets.