The No. 1 sandwich shop is, of course, Subway, with 10 billion restaurants. Excuse me, did I say “billion”? Darn typo. I meant trillion.

The King’s Hawaiian Roast Beef & Swiss sandwich takes what Arby’s does best — slow-cooked roast beef piled high — and then makes it better. By piling the roast beef even higher. The King’s Hawaiian Roast Beef & Swiss stacks one-third more meat than Arby’s regular roast beef sandwich. And then Arby’s makes it twice better by putting all that roast beef on a King’s Hawaiian bun.

Arby’s is calling this “Roast-Beef-Atopia.” There will be a little extra in the marketing staff’s pay envelope for that. Either a cash bonus or pink slip, I haven’t decided.

Here’s the blueprint: thinly-sliced-to-order roast beef, Swiss cheese, pickles and creamy Dijon sauce on an authentic King’s Hawaiian bun.

Total calories: 600. Fat grams: 25. Sodium: 1,640 mg (that’s a lot). Dietary fiber: 2 g. Protein: 34 g. Carbs: 51 g. Manufacturer’s suggested retail price: $4.49 (that’s a little, considering the heft and quality of this sandwich).

The really big thing about the King’s Hawaiian Roast Beef & Swiss sandwich is the bun — an authentic, fluffy, sweet-as-pastry King’s Hawaiian bun. You’ve seen these in the supermarket. They’re puffy like marshmallows, and look like the dinner buns you see at the start of a buffet line.

That’s how they get you at the buffet — they put all the wide, cheap stuff at the start of the line, so your plate is full by the time you get to the peel ‘n’ eat shrimp and steamship round. They don’t get me. I head straight to the end of the line and walk in backward. Of course, everybody in line hates me, but the chances I’ll ever see those tourists in knee socks again are slim.

Arby’s uses real-deal King’s Hawaiian buns — and you know how we feel about recognizable brand names in the drive-thru: It gives us a warm, cozy feeling of familiarity. Hate those 55-gallon drums of mayonnaise with nothing but a bar code on the label. Reminds me of my high-school cafeteria.

For you geography majors, King’s Hawaiian buns are baked in the tropical island paradises of … Torrance, Calif., and Oakwood, Ga. Cue the ukulele music, y’all.

Arby’s roast beef is super-lean, with no gristle or fatty edges. The Swiss melts all gooey, and the Dijon spread has speckles of mustard seed — nice touch. The pickles are cool and crunchy, a wake-up texture call. Everything adds up to a quality sandwich for a decent price. Arby’s is coming on strong lately with bold new flavors, and here’s one more example.

Arby’s also has a stripped-down King’s Hawaiian Roast Beef sandwich, just meat and bun, for $3.99.