Step 1: Season the brisket on all sides with salt, pepper, and red pepper flakes, if using.

Step 2: Set up your grill for indirect grilling or your smoker according to the manufacturer’s instructions. Heat to 225 to 250 degrees. Smoke the brisket until it reaches 160 to 165 degrees, replenishing the wood or smoking chips as needed. Wrap in unlined butcher paper and continue cooking until the brisket is jiggly and has reached 190 to 195 degrees (about 15 hours total, but it depends on the brisket). Transfer to a cooler for at least 1 hour.

Step 3: In the meantime, make the Horseradish Cream: Combine the sour cream and enough grated fresh horseradish to tingle your sinuses. (Prepared horseradish—the kind that comes jarred in the refrigerator section of supermarkets—is usually milder.)

Step 4: Make the Grilled Salsa. Cover and refrigerate if not using immediately.

Step 5: When ready to serve, slice the brisket. Put a dab of Horseradish Cream on each tortilla, then top with brisket, sliced fresh avocado, salsa, and fresh cilantro sprigs.