Diary of a Chef · Just Chefn Around

Blueberry Tartlette — Thyme Crème Fraîche, Jalapeño

2 hours + 24 hr crème · ~10–12 tarts

By Diary of a Chef

Ingredients

• 240 mL heavy cream, pasteurized (not ultra-pasteurized)
• 30 mL cultured buttermilk
• 1 tsp fresh thyme, chopped fine
• 2-finger pinch kosher salt
• 1/2 tsp lemon juice
• 300 g all-purpose flour
• 45 g butter, cold
• butter, soft, for spreading the dough
• 45 g neutral oil (avocado or sunflower)
• 6 g fine salt (for the dough)
• 120 g egg whites (no yolk)
• blueberries, cut into perfect halves
• 1 jalapeño
• 2–3 tbsp butter, for the barrier brush

Instructions

1. 1Culture the crème (24 hrs ahead)

   Stir 240 mL pasteurized cream (not ultra-pasteurized) with 30 mL cultured buttermilk in a clean glass jar. Cover loosely and hold on the counter at about 70–75°F for 12–24 hours (a warm kitchen finishes closer to 14 hours). Stir 2–3 times so a skin doesn't form. It's ready when it thickens at least to loose yogurt and smells pleasantly tangy — sour-cream taste is a pass. Funky, bitter, or fizzy: toss it.

2. 2Chill and judge the set

   Stir once, lid tight, fridge at least 2 hours. Judge the set cold, never warm: it should hold a mound or hold inverted in the jar. If it's slumpy, drain in a Claribag or coffee-filter-lined strainer in the fridge 1–3 hours until it pipes. The set is a fragile gel — every stir after this loosens it for good.

3. 3Season the crème

   Day-of, one gentle fold: about 1 tsp chopped thyme, a 2-finger pinch of salt, about ½ tsp lemon. Taste and adjust. Fold once, then hands off.

4. 4Make the dough

   Rub 45 g cold butter cubes and 45 g avocado or sunflower oil into 300 g flour and 6 g salt until it feels sandy, like sablé — no visible butter lumps. Add 120 g egg whites and mix just until a smooth dough forms. Don't overwork.

5. 5Spread, dock, cut, chill

   Spread on parchment to an even 1.5–2 mm — credit-card thin — using an offset and small dabs of soft butter as lubricant. Check thickness at three points with a ruler. Dock all over with a fork. Press-cut rounds with the 2-inch rings and leave the rings on; pull away scrap between them (keep scrap as test pieces for the next step). Chill the tray 20–30 minutes.

6. 6Bake at 375°F, then 325°F

   Preheat 375°F conventional. Bake about 10 minutes to set structure, then drop to 325°F for 20–40 minutes to dry out — start checking at 25 minutes total. Pale gold is correct (no sugar, so they brown slowly). Judge by a cooled snap, not color: a test piece cooled 5 minutes should snap clean with no bendy center and release clean from the parchment. Edges browning too fast? Drop to 300°F and extend. Rings off after a few minutes; cool the discs fully on a rack. Hold airtight.

7. 7Butter barrier

   Melt 2–3 tbsp butter, sit 1–2 minutes, skim the foam, pour off the clear gold only (stop at the milky bottom). Brush the thinnest sheen on the top of each fully cooled disc and let it set — the fridge speeds it. Required for ring-molded assembly so the crème doesn't soak the shell.

8. 8Assemble and lift

   Ring back over the disc. Crème in, 1 cm deep, wall-to-wall, smooth flat. Blueberry halves cut-side up — outer circle pressed gently against the ring wall, seated about halfway into the crème — then fill the center. One jalapeño slice flat, dead center. Chill 15–30 minutes. Warm the ring with your hands a few seconds and lift straight up, slow. Serve promptly — assembled tarts are not a hold. Baked shells keep 2–3 days airtight; crème about a week cold; berries and jalapeño are day-of only.