beat butter and bacon fat til light and creamy. add brown sugar and maple syrup and beat until well combined. add egg and beat until incorporated. sift flour, salt, baking soda and powder together in separate bowl. add some of the flour mix, then some milk, and continue to alternate dry and wet ingredients, ending with dry. mix until just combined. fold in bacon. scoop into cupcake papers and bake at 350 for 18-22 minutes or until toothpick comes out clean. rotate pan in first 15 minutes for even baking.
for frosting: mix syrup and butter until combined. add sugar, a bit at a time, and whip at high speed until combined. sprinkle a small bit of sea salt on top of frosted cupcakes.