Place the peeled and quartered potatoes in a large pot and cover with cold water. Bring to a boil, then reduce heat and simmer for 15 minutes until the potatoes are fork-tender. Drain thoroughly in a colander, then return to the pot. Add the vegan butter and the 1/2 cup of warmed plant-based milk, then mash until you reach your desired consistency—I prefer mine slightly creamy with a few small lumps for texture. Season with salt to taste and set aside.

Heat the 1 cup of plant-based milk in a small saucepan over medium heat until steaming but not boiling. In a small bowl, whisk the flour with 2 tablespoons of water until completely smooth with no lumps—this prevents the sauce from becoming grainy. Slowly pour the flour mixture into the hot milk while whisking constantly to create a smooth, lump-free sauce. Continue stirring for 2-3 minutes until the sauce thickens enough to coat the back of a spoon. Remove from heat and sprinkle in the vegan cheese shreds, stirring until completely melted and smooth. I like to add the ketchup last, stirring it in gently to create those signature red streaks throughout the sauce without fully blending it—this keeps the visual drama of the 'lava' effect.

Divide the mashed potatoes from Step 1 evenly among 4 serving plates. Using the back of a spoon or an ice cream scoop, shape each mound of potatoes into a volcano shape by creating a well or indentation at the top—make the indentation deep enough to hold the sauce without it spilling over immediately. Arrange the thawed peas and broccoli florets around the base of each potato volcano.

Spoon or carefully pour the warm cheese sauce from Step 2 into the indentation at the top of each potato volcano, allowing it to flow down the sides like lava. Serve immediately while the sauce is warm and the potatoes are at their best.