Make the chimichurri

• Finely chop the parsley, jalapeño, habanero, garlic, orange bell pepper and yellow bell pepper.
• Combine in a bowl with the red wine vinegar, olive oil, lemon juice, lemon zest, red chili flakes, salt and pepper.
• Stir well and let the chimichurri rest so the flavors meld.

Season and grill the tri-tip

• Season the tri-tip generously with salt and pepper.
• Grill over high heat, turning, until nicely charred and cooked to medium-rare.
• Rest the steak before slicing.

Prepare the sandwich components

• Mix the horseradish with the Boursin cheese.
• Slice the heirloom tomatoes and the mozzarella.
• Slice the rested tri-tip thinly against the grain.

Assemble the sandwich

• Spread the horseradish Boursin on the focaccia halves.
• Layer the sliced tri-tip, mozzarella, heirloom tomato and basil.
• Spoon over the chimichurri, close the sandwich and slice to serve.