Step 1: Prepare the Birria Beef

1. Toast the Dried Chilies

• Heat a dry skillet over medium heat. Toast the guajillo and ancho chilies for about 30 seconds per side until fragrant.
• Transfer to a bowl and cover with hot water. Let soak for 10 minutes.

2. Blend the Sauce

• In a blender As an Amazon Associate, I earn from qualifying purchases made through links on this site., combine the soaked chilies, chipotle peppers in adobo, onion, garlic, vinegar, and all the spices with 1 cup of beef broth.
• Blend until smooth.

3. Cook the Birria Beef

• Slow Cooker: Add the beef, blended sauce, and remaining beef broth. Cook on low for 8 hours or high for 4 hours.
• Instant Pot: Cook on high pressure for 45 minutes, then allow a natural release for 15 minutes.

4. Shred the Beef

• Remove the beef and shred with two forks.
• Return it to the broth and let it absorb the flavors.

Step 2: Prepare the Chipotle Horseradish Aioli

1. In a small bowl, whisk together mayonnaise, horseradish, lemon juice, Dijon mustard, garlic powder, chipotle pepper, salt, and pepper.
2. Cover and refrigerate until ready to use.

Step 3: Make the Onion Strings (Optional)

1. Place thinly sliced onions in a bowl and cover with buttermilk. Let soak for at least 15 minutes.
2. In another bowl, mix flour, cornstarch, salt, black pepper, and smoked paprika.
3. Heat oil in a skillet or deep fryer As an Amazon Associate, I earn from qualifying purchases made through links on this site. to 350°F.
4. Dredge the soaked onions in the flour mixture, shaking off excess.
5. Fry in batches for 1-2 minutes, until golden brown and crispy.
6. Transfer to a paper towel-lined plate to drain.

• Alternative: Use store-bought crispy fried onions for convenience.

Step 4: Assemble the Sliders

1. Preheat oven to 375°F.
2. Slice the brioche slider buns in half and place the bottom halves on a baking sheet.
3. Spread a layer of chipotle horseradish aioli on each bun.
4. Layer shredded birria beef evenly over the buns.
5. Sprinkle generously with shredded cheese.
6. Add crispy onion strings (if using).
7. Place the top buns back on and press down gently.
8. Mix melted butter, garlic powder, and chopped cilantro. Brush over the tops of the sliders.
9. Bake for 10-12 minutes, until the cheese is melted and the buns are golden brown.

Step 5: Serve

• Serve the sliders hot with a side of birria broth for dipping.
• Garnish with extra crispy onion strings or fresh cilantro if desired.

Healthier Version (Optional)

For a lighter take on these sliders:

• Use whole wheat slider buns instead of brioche or Hawaiian buns.
• Substitute Greek yogurt for mayonnaise in the aioli.
• Opt for baked onion strings instead of fried, or use store-bought crispy onions sparingly.
• Choose low-fat cheese or reduce the amount of cheese used.

Use leaner cuts of beef or swap for shredded chicken breast for a lower-fat alternative.