I was curious about the unique flavor of Bossa from Deep Cello Roasters and how they suggested pulling the shots of it, so I wrote to ask. I was quite pleased to get the following detailed answer from Justin Kagan and I thought others would enjoy reading it, too…
"Bossa is about 65% pulped natural Brazil (microlot Fazenda Esperança from a farmer I know down in Minas Gerais), a particularly nutty and chocolatey coffee at the relatively light-medium roast profile I give it. As a straight shot is is even more nutty/chocolatey but less complex aromatically and finish-wise, hence my blending with other components to give some other mid- and top-notes. Recently I have been pairing the complex 3-way processing El Salvador Finca El Manzano because of the sweet spot, apricot-y/agave mid-palate, and resultant sweet finish with a medium hint of acidity (mostly from the washed portion of the 3-way, which itself constitutes about 15% of the El Sal...it's about 50% natural process, 35% pulped natural, and 15% washed,). The balance is a natural process Ethiopia Limu from a fine producer, Nigusie Lemma. The Limu is also chocolatey and blueberry/raspberry toned, quite overwhelming as a SO spro, but just right in Bossa proportions to be present.
Sensory experiences are very personal, even beyond the mere technical variance from machine to machine. I for one perceive bacon first as sweet rather than salt, broadly speaking, and also have a prominent sweet tooth...perhaps this is why I choose certain coffees over others for espresso. But it definitely informs my roast profile preferences and selection of certain varietal and processing...tending towards naturals and pulped naturals. Washed coffees generally have enough acidity to wash out perceivable high-note esters and are frankly easier to roast, per se, arguably make" user-friendly" espresso. Problem is the acidity for me....I don't like overly tannic/puckery explosions when drinking 'spro...can get that from a Central American drip, or a Kenyan (of course SO washed espresso...DEFINITELY not what I drink, though I do run every individual coffee I buy through the macchina..cuz ya never know...).
My preference for classical Euro-style espresso came from my experiences in Italy, although coffee there tends to be darker roasted, uses more washed Central American coffees (Guatemalans in particular), and a good bit more bitter (perhaps this is why they like sugar so much in their spro). But the really good shots there always had an inherent sweetness which I wanted to duplicate back here the minute I started roasting. I have taken things more extremely in tweaking, especially with lightening up the roast profiles to interpolate the naturally-occurring sugar content.
I think owing to roast level and the above jazz about the Bossa your starting point should be close to 201 degrees, and about a 26 second shot if you're not getting much blonding after about 20 seconds. (this might apply to most lighter-medium roasted coffees).
I'd try similar temps for the BlackTie, which is about 45- 50% Brazil but also includes two washed coffees (Yirgacheffe and a different El Salvador).
If you ever try Nostromo, which is a way darker roast, I'd dial back to 199 max if you want to get it on the sweet side and not exaggerate the toastier side of the roast profile.
If you can squeeze 18 grams in your machine without too hard a tamp to nestle into the group and pull a 25-26 second shot with pre-infusion you'll be very happy."
It is good to know there are people out there even more fanatical about great coffee than I am!