Creamy Orange Filling: In bowl of stand mixer or with electric beaters, beat butter until creamy. Beat in marmalade and cardamom. Add half of the icing sugar; blend until smooth. Add remaining icing sugar; blend until thick and spreadable. Transfer to a small bowl; cover and refrigerate.
Meanwhile, in a food processor, pulse pistachios until finely chopped. Set aside. Wipe out food processor; add icing sugar, almonds and salt. Pulse until powdery (skip this step if using almond flour; simply whisk together in a bowl instead).
In bowl of stand mixer or large bowl with electric beaters, whisk egg whites until foamy. Gradually beat in sugar until firm and glossy soft peaks form. Fold in enough food colouring to tint mixture light green. Fold in one-third of the almond mixture until just combined; lightly fold in remaining mixture.
Using a piping bag fitted with a small plain tip or a resealable plastic bag with one corner snipped off, pipe meringue in 2 tsp (10 mL) rounds, about 1 inch (2.5 cm) wide and spaced 1 inch (2.5 cm) apart, on parchment-paper-lined baking sheet (use damp finger to flatten tops, if necessary). Sprinkle tops with chopped pistachios. Let stand for 30 minutes.
Bake, 1 sheet at a time, in centre of preheated 275°F (140°C) oven until firm, dry and cracked around bottom edges, 14 to 16 minutes. Let cool on pan on rack.
Meanwhile, in a small heatproof bowl set over a small saucepan of hot (not boiling) water, melt chocolate, stirring, until beginning to melt. Remove from heat and continue stirring until melted and smooth. Let cool slightly.
Spread the flat side of each cookie with a thin layer of melted chocolate; let stand, flat side up, until chocolate sets, about 10 minutes.
Spread about ½ tsp (2 mL) of the Creamy Orange Filling on chocolate layer of half of the macarons. Sandwich with remaining macarons. Let stand until set, about 10 minutes.
Makes 50 macarons Per macaron: 60 calories, 1 g protein, 3 g fat (1 g saturated fat), 7 g carbohydrates, 0 g fibre, 3 mg cholesterol, 19 mg sodium
Per macaron: 60 calories, 1 g protein, 3 g fat (1 g saturated fat), 7 g carbohydrates, 0 g fibre, 3 mg cholesterol, 19 mg sodium