Preheat the oven to 150 degrees.
Trim the leaves from the rhubarb and carefully remove any brown edges from the ends. Rinse the stalks thoroughly. Cut them into pieces of about 3 cm. Place the rhubarb pieces, sugar, vanilla seeds and pod in an ovenproof dish and mix well. Place the dish in the oven for approx. 25 minutes, until the rhubarb is tender. Stir gently halfway through. Remove the dish and leave the compote to cool on the kitchen worktop.
Crush the cardamom pods in a mortar, remove the black seeds from the pods and grind them to a powder in the mortar. Discard the green husks.
Whisk the egg yolks, cardamom powder and icing sugar together in a bowl for about 8–10 minutes, until the mixture is white and very frothy.
Whip the cream to soft peaks in another bowl, gently fold everything together, then place the ice cream mixture in a bowl and freeze for at least 4 hours.
Remove the ice cream and let it soften in the fridge for about 15 minutes before serving.
Whisk together the eggs, cream, syrup, vanilla seeds and sugar in a bowl.
Dip the bread in the mixture and leave it to soak for a couple of minutes. Remove the slices of bread and then coat them in the cinnamon sugar. Fry the slices of bread in butter in a hot frying pan until they are golden and crispy.
Serve the warm French toast with rhubarb compote and cardamom ice cream on plates, sprinkling with a few chopped, toasted almonds and edible flowers if desired.
