Cut the potatoes into 1/4 inch thick fries and soak them in cold water for 30 minutes to remove excess starch. Preheat the oven to 425°F and line two baking sheets with parchment paper.
Drain the fries and dry them very well with a towel. Toss with the cornstarch, olive oil, and salt, then spread them in a single layer across both baking sheets.Bake for 35-40 minutes, flipping halfway through, until golden and crisp.
While the fries bake, brown the ground beef and onion in a skillet over medium high heat for 7-8 minutes. Drain the excess fat, then stir in the garlic, chili powder, and cumin for 1 minute.Add the tomato sauce, beef broth, and salt, and simmer for 15 minutes until thick.
For the cheese sauce, melt the butter in a small saucepan over medium heat and whisk in the flour for 1 minute. Slowly whisk in the oat milk and simmer for 2-3 minutes until thickened.Lower the heat and whisk in the dairy free cheddar a handful at a time, then add the nutritional yeast, Dijon mustard, garlic powder, smoked paprika, salt, and cayenne until silky smooth.
Pile the hot fries onto a platter, spoon the chili over the top, and drizzle generously with the cheese sauce. Finish with green onions and jalapeno slices and serve right away.