Prep the slow cooker. Line the insert with parchment so it comes up the sides, or coat it well with nonstick spray. This helps you lift the loaf out cleanly.
Combine dry ingredients. In a large bowl, whisk the flour, baking powder, salt, sugar, garlic powder, and smoked paprika until evenly mixed.
Add beer and butter. Pour in the beer and melted butter.
Stir with a spatula until just combined. The batter will be thick and slightly shaggy—don’t overmix.
Fold in cheese (and chives). Stir in the cheddar and chives until evenly distributed. Reserve a small handful of cheese for the top if you like a cheesy crust.
Fill the cooker. Spoon the batter into the lined insert.
Smooth the top lightly with a spatula. Sprinkle remaining cheese on top if using.
Cook on High. Cover and cook on High for 2 to 3 hours, until the top is set and a toothpick inserted in the center comes out clean. Start checking at 2 hours; every cooker runs a bit different.
Vent for a crust. For the last 20 to 30 minutes, wedge a wooden spoon under the lid to vent steam.
This helps the top firm up and develop a light crust.
Finish with butter. Brush the warm loaf with a little melted butter for sheen and flavor.
Cool before slicing. Lift the bread out using the parchment and let it cool on a rack for at least 20 minutes. Slicing too early can make it gummy.