In a small saucepan or microwave oven, melt butter and let cool to room temperature.
In a small mixing bowl, beat eggs, candy caps or extract, and salt until fully combined.
Beating constantly, gradually add sugar. Continue beating for five to ten minutes at high speed until mixture is thick and pale and ribbons form in bowl when beaters are lifted.
Sift flour into egg mixture 1/3 at a time, gently folding after each addition.
Pour melted butter around edge of batter.
Quickly but gently fold butter into batter.
Divide batter evenly among the madeleine molds. I found that the easiest way to do this was to use two spoons - one to get a spoonful of batter from the bowl, and one to scrape the batter off of the spoon and into the pan. (If your madeleine pan is non stick, you do not need to grease the pan first. If your pan is not non-stick, butter the pan before filling the molds.)
Bake 14 to 17 minutes, or until cakes are golden and the tops spring back when gently pressed with your fingertip.
Eat the madeleines on their own, dunked in coffee or hot chocolate, or spread some frosting on them.