Combine baking mix, nuts, and currants in a large bowl and mix until evenly combined. Make a well in the center of the dry ingredients and add the beer, eggs, and vegetable oil. Stir dry ingredients into wet ingredients until just moistened. (Don’t overmix or the pancakes will be tough. The batter should be lumpy.) Heat a cast iron skillet over medium heat on a camping stove or over a campfire fitted with a grilling grate. Test to see if the pan is hot enough by sprinkling a couple of drops of cold water in it: If the water bounces and sputters, the pan is ready to use; if it evaporates instantly, the pan is too hot. Add 1 tablespoon oil to the pan and swirl to coat. Ladle about 1/4 cup batter into the pan for each pancake. (You should be able to fit 3 to 4 pancakes at a time.) Cook until pancakes rise slightly and form lots of bubbles on top, about 3 to 4 minutes. Flip and cook on the other side until bottoms are golden brown, about another minute. Repeat with remaining batter, adding 1 tablespoon oil between batches if the pan seems dry. Serve immediately with butter and maple syrup.