To a small pot over medium-high heat, transfer the mixed berries, jam, hot water and sugar, and stir constantly for a couple of minutes until you have a berry sauce, then turn off the heat and set aside.
Whisk the eggs and pour half into a dish or container large enough to hold the slices of bread. Dip one slice of bread into the container, turn it over, ensure that it’s covered in egg, lift it up, dip the other slice in, turn it over, then pop the other slice of bread on top.
In a frying pan that’s big enough to hold two slices of bread, heat two teaspoons of butter over medium heat. Use a wide spatula or fish slice to lift each slice of bread out of the egg and into the frying pan.
Fry the bread slices first on one side until golden brown, then turn the slices over, pressing down on the bread lightly with the spatula, and fry the other sides until golden brown. Slide them out of the pan and transfer them to a plate. Repeat with the other slices.
Scoop the berries and sauce out of the pot and onto the toast, along with dollops of fresh cream, whipped cream or sour cream, and use a hand-held sifter to sprinkle icing sugar onto the plates. Serve immediately.