Preheat the oven to 110°C (gas 1/4). Gently heat the milk and cream in a saucepan and bring to just below boiling point. Immediately remove the pan from the heat.
Place the egg yolks, sugar and mixed spice in a large mixing bowl. Whisk with an electric hand mixer until the mixture is pale and frothy.
Slowly add the hot creamy milk to the egg yolk mixture, stirring to mix. Strain the custard into a jug, through a sieve.
Pour the custard mixture into six 150ml heatproof individual dishes or ramekins. Place on a baking sheet and bake for 1¼ hours or until just set.
Remove from the oven and leave to cool at room temperature, then place in the fridge for at least 2 hours or overnight, to chill thoroughly. (The desserts must be very cold when put under the grill in the next step to achieve the contrast between hot and cold, creamy and crunchy.)
A few minutes before serving, preheat the grill to high. Sprinkle 2 tsp of sugar evenly over the top of each dessert and place them under the grill for 30–40 seconds until the sugar caramelises. Cool slightly, then serve immediately with small dessert biscuits. (For crunchy tops, do not put the desserts back in the fridge, or the sugar will dissolve.)
Make the most of the low oven temperature to make meringues, using the leftover egg whites.