Put your Madeleine pans in the freezer for at least 1 hour. They can just sit in there until you're ready to prepare them.
Place all the butter in a large pot over medium heat. Bring to a boil, reduce the heat to medium-low and simmer until toasty and brown. Be careful - you don't want to burn it. When it's finished it'll be amber and smell delicious and nutty. Spoon 3 Tbsp into a bowl and set aside. Allow the remaining butter in the pot to cool slightly.
In a large bowl whisk together the sugar and flour. Set aside.
In a smaller bowl, whisk together the eggs, pure vanilla extract, pinch of salt and lemon juice until frothy. ***If making the lemony earl grey Madeleines, also mix in the lemon zest and tea at this stage. If making the vanilla bean Madeleines, mix in the vanilla seeds.
Pour the wet ingredients into the dry ingredients and fold together with a spatula until just combined. Add the slightly cooled butter from the pot. It may take a moment or two for the batter to absorb the butter completely but as soon as it does, stop mixing. Do not over-work the batter.
Cover the bowl with plastic wrap or a plate and place in the fridge to cool for at least 1 hour or up to over-night.
Prepare your frozen Madeleine pans. Remove them from the freezer and gently brush the reserved 3 Tbsp of browned butter into the molds, careful to get it in all the curves and crevices. Using a fine mesh strainer, dust the extra flour over the butter to coat completely. Turn the pans upside down over the sink and gently knock any excess flour off. Place the prepared pans back in the freezer for at least 10 minutes.
Pre-heat your oven to 350 degrees F.
Remove the batter from the refrigerator and one pan from the freezer. Fill each mold in the madeleine pan with 1 tablespoon of the batter. Place back in the freezer while you fill the second pan.
When both pans are ready, place them in the oven and bake 12 - 15 minutes or until the Madeleines are browning slightly on the edges and are puffy in the middle. When you gently press the center of one with your finger it should bounce back.
Remove the Madeleines from the oven and let sit in the baking pans for about 5 minutes. Using a spoon or fork, gently lift each Madeleine from the pan and set on a wire rack to cool.
If making the Lemon Earl Grey Madeleines:
Pour the powdered (confectioners) sugar in the fine mesh strainer and gently dust the Madeleines before serving.
If making the Vanilla Bean + Chocolate Almond Dipped Madeleines:
Place a water filled double boiler over medium-high heat. A pot with a cup or two of water and a non-reactive bowl works well - just make sure the water doesn't touch the bottom of the bowl. Add the dark chocolate and 1 Tbsp of butter. Mixing constantly, heat through until chocolate is melted. Remove from the heat.
Gently dip the end of each Madeleine into the chocolate and then into the almonds. Place on a wire rack for the chocolate to set. If you put them in the fridge once you're done they'll set faster.