Make the shredded chipotle beef (can be prepared up to 2 days in advance): place 1 tablespoons vegetable oil and 2 tablespoons butter in a large heavy-bottomed pot or Dutch oven over medium-high heat. Heat until the butter foams.
Add 2 medium garlic cloves, minced, and 1 medium yellow onions, medium dice to the pot. Season with salt and pepper to taste. Cook, stirring occasionally, until the onions are translucent and starting to brown at the edges, about 7 minutes.
Add 2 chopped chipotles in adobo sauce, plus 1 teaspoon sauce, 3 teaspoons ground cumin, 1 tablespoons smoked paprika, 1 tablespoon chili powder, and 1/4 teaspoon cinnamon. Stir to combine and cook about 1 minute, until fragrant.
Add 1 pounds beef chuck roast, 1 tablespoon kosher salt, and 1 16 oz. ounce can crushed tomatoes to the pot. Bring the mixture to a boil, then reduce the heat to the lowest setting, cover, and simmer gently for 4–5 hours, until the roast is very tender and shreds easily.
Remove the roast from the pot and let it cool slightly. Using two forks, shred the beef. Return the shredded beef to the pot and stir it into the cooking liquid to absorb flavor. Taste and adjust seasoning with salt and pepper if desired.
Assemble the filling: in a large bowl, combine the shredded chipotle beef, 3 cups scrambled eggs, 3 cups cooked tater tots, and 1/4 cup chopped green onions. Gently toss to combine.
Portion the filling as desired and serve immediately, or cool and refrigerate the beef (or the mixed filling) for up to 2 days. Reheat gently before serving.