7 base sauces that change everything (and save any meal)

Have on hand: olive oil, vinegar or lemon, salt, pepper, garlic, mustard, and a fresh or dry herb.
Use jars with lids: shake, emulsify, and store in the same container.
Always taste at the end: the sauce "wakes up" when you adjust salt + acid in the last 10 seconds.
Heat and emulsion don't always get along: if a sauce breaks, lower the temperature and whisk calmly.
If in doubt, apply the rule: "it lacks spark" = acid; "it lacks depth" = salt/umami.

Express base (mayo): 1 egg (or 2 yolks) + 1 tsp mustard + 1 tbsp lemon/vinegar + salt; add 200–250 ml oil in a stream while blending.
Mild aioli: add 1 garlic clove without the germ (or roasted) so it doesn't repeat.
Plan B if it breaks: in another glass, put 1 tbsp water or lemon and incorporate the broken mayo little by little while beating.
Lighten in 10 seconds: 1–2 tbsp yogurt or water to turn it into a creamy sauce.
Uses: sandwiches, baked vegetables, potatoes, potato salad, battered fish, burgers.

Roux: 30 g butter + 30 g flour; cook 2–3 min to remove flour taste.
Add 500 ml hot milk little by little, whisking constantly, until thickened.
Fine adjustment: salt + nutmeg; for extra flavor, white pepper and a touch of parmesan.
Anti-lumps: if they appear, blender 10 seconds or fine strainer (zero drama).
Uses: lasagnas, croquettes, gratins, baked cauliflower, cannelloni, homemade "mac & cheese".

Base: plain yogurt (Greek or regular) + lemon + salt + very minced garlic + herbs (dill, mint, parsley).
For "dip" texture: Greek yogurt; for more fluid version: add 1–2 tbsp water.
Super combo: grated and drained cucumber (tzatziki style) for spiced dishes.
Quick adjustments: more lemon for spark; olive oil to round out; cumin for Mediterranean touch.
Uses: homemade kebab, salads, raw vegetables, roasted potatoes, falafel, fish tacos.

Batch: prepare 2–3 sauces on Sunday and combine during the week (pasta + pesto; vegetables + yogurt; chicken + soy-ginger).
Fridge: vinaigrette 5–7 days; tomato 4–5 days; yogurt 3–4 days; mayo/aioli 2–3 days; pesto 4–5 days (better with oil on top).
If a sauce is too thick, lighten with hot water (bechamel) or cold water/lemon (vinaigrette).
If it's bland, add salt and a drop of acid; if it's strong, balance with fat or sweet.
Label the jar and you're done: cooking "tasty" becomes automatic.