Place butter in a small microwave-safe bowl and heat on high until melted. Set aside until cooled.
Sift and mix flour, salt, baking powder, and matcha and set aside.
Place egg and sugar in a bowl of a stand mixer fitted with the paddle attachment. Mix on medium-high speed for 8-10 minutes. Mixture should be thick and pale.
Add vanilla extract and honey and mix for another 30 seconds.
Fold in dry ingredients using a spatula. Do not overmix. Then, fold in melted butter and incorporate into batter.
Cover and chill batter for 30 minutes to 1 hour.
To grease the madeleine pan, melt 2 tsp. butter and use a pastry brush to lightly brush the madeleine molds with melted butter. Then, lightly dust them with some flour.
Transfer greased and dusted madeleine mold pan to a refrigerator and chill for at least 20 minutes.
In the meantime, preheat the oven to 190°C (375F)
Divide madeleine batter between 12 molds (fill ⅔-¾ of the mold). NOTE: If you have extra batter or you will be reusing the mold for a second batch, you will need to re-grease, dust, and re-chill the madeleine pan. Bake madeleines for 9-12 minutes until puffed up and hunched at the top and edges turn slightly golden brown.
Transfer to a cooling rack to cool completely if coating with chocolate. Otherwise, lightly dust with powdered sugar.
Topping: melt chocolate in microwave-safe bowl and coarsely crush hazelnuts. Dip madeleines in melted chocolate, then sprinkle with crushed hazelnuts. Transfer to a wire rack and chill until chocolate has set.