Shortbread Lab433 recipes

Shortbread Lab

Three styles in 433 shortbread recipes

Leave the recipe names aside and group the 433 recipes by their 4 ingredient ratios alone, so that recipes built alike land together. Each group is named only by the numbers: the ingredients where its recipes sit furthest from the middle of all 433.

The data splits best into three groups, and they separate: a silhouette of 0.34, on a scale where 0 is no separation and 1 is complete. They still touch at the edges, so a recipe near a boundary could sit in either.

The recipes on one map

Every recipe, placed on the two directions along which the ratios vary most (a principal component projection). Close dots are recipes built alike. The lettered rings mark the middle of each group.

ABC
Across →
More butter, sugar and salt to the right; 38% of the variation.
Up ↑
More salt, less starch upward; 26% of the variation.

The three groups

AClose to the overall median

272 recipes · 63% of all 433 · median oven 350°F (175°C), 17 min

Where it differs from all recipes

  • Sugarmedian 35% vs 40% for all

    average rank: 39th percentile of all recipes

  • Buttermedian 76% vs 81% for all

    average rank: 40th percentile of all recipes

  • Saltmedian 0.1% vs 0.4% for all

    average rank: 39th percentile of all recipes · none in 48% (all recipes 36%)

Its median recipe, at 250 g flour

Median recipe of group A in grams, against the median of all recipes
IngredientGroup AAll
Butter190 g200 g
Sugar90 g100 g
Starchnonenone
Salt0.5 g1 g

Each line is the group's median for that ingredient, scaled to 250 g of flour.

Closest to the middle of the group

BMore salt and sugar

116 recipes · 27% of all 433 · median oven 350°F (175°C), 18 min

Where it differs from all recipes

  • Saltmedian 1.2% vs 0.4% for all

    average rank: 76th percentile of all recipes · none in 9% (all recipes 36%)

  • Sugarmedian 56% vs 40% for all

    average rank: 74th percentile of all recipes

  • Buttermedian 89% vs 81% for all

    average rank: 61st percentile of all recipes

Its median recipe, at 250 g flour

Median recipe of group B in grams, against the median of all recipes
IngredientGroup BAll
Butter220 g200 g
Sugar140 g100 g
Starchnonenone
Salt3 g1 g

Each line is the group's median for that ingredient, scaled to 250 g of flour.

Closest to the middle of the group

CMore starch and butter

45 recipes · 10% of all 433 · median oven 350°F (175°C), 15 min

Where it differs from all recipes

  • Starchmedian 25% vs 0% for all

    average rank: 91st percentile of all recipes · none in 6% (all recipes 83%)

  • Buttermedian 102% vs 81% for all

    average rank: 84th percentile of all recipes

Its median recipe, at 250 g flour

Median recipe of group C in grams, against the median of all recipes
IngredientGroup CAll
Butter255 g200 g
Sugar105 g100 g
Starch65 gnone
Salt1 g1 g

Each line is the group's median for that ingredient, scaled to 250 g of flour.

Closest to the middle of the group

How the groups are found

Each ratio is converted to a z-score (how many standard deviations a recipe sits from the mean), capped at 3 so one extreme recipe cannot claim a group, and k-means sorts the recipes into k groups, trying k from 2 to 4. Each k runs from 16 fixed starting points and keeps the tightest result, so the page is the same on every build. No group may hold fewer than 44 recipes.

The number of groups is the one with the best silhouette, which compares how close each recipe is to its own group with how close it is to the next one. By number of groups: 2 groups 0.31 · 3 groups 0.34 · 4 groups 0.27. At 0.25 or more the page calls the groups separate; from 0.18 to 0.25, overlapping; under 0.18, no clear styles.

A group's name lists the one to three ingredients where its recipes rank furthest from the middle of all 433, on average. “More” and “less” are relative to the whole dataset, and the names say nothing about texture or taste, which the ratios alone do not show. The median recipe of a group is, like the typical recipe on the overview, the middle of each ingredient separately, not one real recipe. The recipes listed under each group are the ones nearest its center, at most two from any one site.