Almond-Clams
I belive they used clam shell copper cake moulds like these in the 18th century.
Tin moulds of today does not resemble a clam in any other way than the scalloped edge.
Instead of this kind of cake moulds you should be able to use madeleine tins.
150g almonds
7 bitter almonds
30 ml water
150g flower
150g confectioners sugar
100g unsalted butter
Blanche, skin and grind almonds finely using a pestle and mortar, adding small amounts of water so as not to make it oily, nor too wet. Combine with flower, sugar and butter. Grease your cake moulds with butter before lining them with the pastry. The recipe says to use the back of a small spoon, but I just use my thumbs to press pastry into the groves/folds of the mould. Bake at 175°C in the middle of the oven for approximately 8 minutes. Knock the shells out of their moulds while still warm. If that does not work, pry them out gently with the tip of a small knife.
This makes 40 shells. The recipe does not mention how to serve them, but they are traditionally served with whipped cream and jam or berries, if the season allows it.
Cajsa Warg, 1755, p 518