To make the pancakes, sift the flour into a bowl with a small pinch of salt and sugar and make a well in the middle. Crack the eggs into the well and whisk them into the flour. Mix the sour cream with 150ml water and pour this in too, whisking to incorporate until you have a smooth batter the consistency of double cream – add a splash more water or milk if needed. Leave to rest for 30 mins.
For the sauce, whisk the cornflour with the orange juice until smooth. Warm it in a pan, stirring to thicken, for around 2 mins. Add the marmalade, amaretto and lemon juice and cook for a few mins more. Gradually add the butter, whisking until you have a glossy sauce.
Stir the melted butter into the batter, then grease a non-stick pan and place over a high heat. Stir the batter, then ladle some into the pan. Swirl it around the pan and cook until it slips away from the pan when you shake it (a couple of mins). Use a spatula to flip the pancake and cook the other side until it comes away and is golden and caramelised in patches. Remove to a plate and keep warm, either covered in foil or in a low oven. Repeat with the rest of the batter until you have a pile of pancakes. Dust each one with a little caster sugar and top with the marmalade amaretto sauce. Fold into four, top with a bit more sauce, scatter over the toasted almonds and serve.