Sift the flour into a bowl, then stir in the sugar. Add the egg and a little milk, and whisk to make a stiff batter. Beat in the remaining milk.
Heat a little butter or oil in an 18 cm (7 inch) pan until it starts to smoke. Pour off the excess and pour in a little batter, tilting until the base is thinly coated. Cook for 1–2 minutes until the underside begins to turn golden.
Flip the pancake with a palette knife and cook for a further 30–45 seconds on the second side. Slide out of the pan and make the remaining pancakes.
Mix the ginger in a bowl with the sugar, ricotta, raisins, white chocolate and cream. Place spoonfuls of the filling in the centres of the pancakes and fold them into quarters, enclosing the filling.
Place the pancakes in a lightly greased ovenproof dish and dust with sugar. Heat in a preheated oven, 200°C (400°F), Gas Mark 6, for 10 minutes.
Dissolve the caster sugar in the water, then boil rapidly for 1 minute. Remove from the heat and add the chocolate. Leave until melted, then stir in the butter for a smooth glossy sauce to serve with the hot filled pancakes.