In a medium saucepan, combine the whole milk, double cream, half of the caster sugar, milk powder, honey, Maldon sea salt, and vanilla paste. Heat gently over medium heat until steaming but not boiling, stirring occasionally.

Meanwhile, in a separate bowl, whisk the egg yolks with the remaining sugar until light and fluffy, about 4-5 minutes.

Gradually add half of the hot cream mixture into the egg yolks, whisking constantly. Pour back into the saucepan and cook over low heat until the custard thickens.

Remove from heat and stir in condensed milk and almond extract. Strain through a fine sieve and cool to room temperature. Refrigerate for at least two hours.

Preheat oven to 180°C. In a baking dish, combine chopped rhubarb, remaining sugar, lemon juice, and optional grenadine. Roast for about 30 minutes until soft and syrupy.

Once cooled, blend the rhubarb until smooth and mix with half of the cooled custard. Fold in the remaining custard and refrigerate overnight.

Pour the chilled mixture into an ice cream maker and churn according to instructions for 20-30 minutes. Transfer to an airtight container and freeze for at least four hours.