Make the pickled carrots: In a small saucepan, combine the vinegar, water, sugar and salt over high heat. Bring to a boil, stirring to dissolve the sugar and salt. Place the carrots in a heatproof bowl and cover with the pickling liquid. Let cool completely and set aside.
Meanwhile, make the carrot salad: In a spice grinder, combine the toasted coriander, fennel seeds, peppercorns, caraway seeds and cumin seeds. Grind into a fine powder, then transfer to a small saucepan along with the carrots, orange juice and agave. Cook over medium-high heat until the carrots are tender and the juice has reduced, 3 to 4 minutes. Remove from the heat and transfer to a bowl, then let cool completely. Once cool, stir in the olive oil and apple until incorporated. Season with salt, then set aside.
Make the carrot-harissa spread: Bring a medium pot of salted water to a boil. Add the carrots and cook until tender, 5 to 6 minutes. Drain the carrots and transfer to a blender with the olive oil, lemon juice and harissa. Purée until smooth, then transfer to a bowl and set aside.
Make the whipped tofu: In a clean blender, combine all the whipped tofu ingredients and purée until smooth. Transfer to a squeeze bottle or small piping bag.
Assemble the toast: Spread ¼ cup of the carrot spread onto each piece of toast, then, using a slotted spoon, top with ¼ cup of the carrot salad. Pipe dots of the whipped tofu around the toast, then garnish with the pickled carrots and carrot-top leaves. Slice in half crosswise, then serve.