Fresh herbs are the secret weapon of exceptional cooking, and the mortar and pestle is the ideal tool for unlocking their full potential. Unlike chopping with a knife—which cuts plant cells cleanly—grinding ruptures cell walls and releases aromatic essential oils that would otherwise remain locked within the plant tissue. This fundamental difference transforms how herbs interact with your dishes, creating depth of flavour that simply cannot be achieved through other means.

🔑 Key Takeaway

Grinding herbs releases up to three times more aromatic compounds than chopping, because the crushing action ruptures plant cells rather than cutting them cleanly.

Understanding Herb Structure

Before diving into techniques, it helps to understand why grinding works so effectively. Fresh herbs contain essential oils stored in specialised cellular structures. Basil leaves, for instance, contain tiny glands on their surface filled with aromatic compounds. When you crush basil in a mortar, you're breaking open these glands and releasing the oils directly into your preparation.

Different herbs have different structures, which means they respond best to specific grinding approaches:

  • Tender-leaf herbs (basil, mint, coriander leaves): Require gentle bruising rather than aggressive grinding
  • Woody herbs (rosemary, thyme, sage): Need more aggressive action to break down fibrous stems
  • Resinous herbs (oregano, marjoram): Benefit from grinding with salt to help extract oils

The Foundation Technique: Salt Grinding

Professional chefs almost always start herb pastes with salt—not just for flavour, but because salt crystals act as an abrasive that helps break down plant material more efficiently.

Basic Salt Grinding Method

  1. Add a generous pinch of coarse salt to your mortar
  2. Add your herbs in small batches
  3. Use a pressing and twisting motion rather than pounding
  4. The salt will draw moisture from the herbs, creating a paste
  5. Continue until you reach desired consistency

💡 Pro Tip

Use flaky sea salt or kosher salt rather than fine table salt. The larger crystals provide better abrasive action and give you more control over the final salinity of your dish.

Herb-Specific Techniques

Basil: The Pesto Perfect Approach

Basil is perhaps the most commonly ground fresh herb, thanks to its starring role in classic pesto. The key is gentle handling to prevent oxidation (browning).

  • Use only the leaves—stems can be bitter
  • Work quickly; basil oxidises rapidly once bruised
  • Start with salt and garlic as a base before adding basil
  • Use a gentle pressing and smearing motion
  • Add pine nuts and cheese only after the basil is properly broken down
  • Drizzle olive oil continuously while grinding to prevent oxidation

Coriander (Cilantro): Roots, Stems, and Leaves

Coriander is unique because every part of the plant can be ground, each offering different flavour profiles:

  • Roots: Most intense flavour; pound first with garlic and peppercorns for Thai curry pastes
  • Stems: Good flavour, less delicate than leaves; grind with moderate pressure
  • Leaves: Add last and grind briefly to preserve colour and fresh flavour

🔑 Thai Technique

For authentic Thai curry paste, always start by pounding coriander roots with garlic. This combination forms the aromatic foundation of most Thai curry pastes and is difficult to replicate with a food processor.

Mint: Preserving Brightness

Mint's volatile compounds dissipate quickly, so speed is essential:

  • Work in small batches for better control
  • Add sugar for sweet applications—it helps preserve colour and acts as an abrasive
  • Grind just before using; mint paste darkens within minutes
  • Combine with a small amount of lemon juice to help preserve bright green colour

Rosemary and Thyme: Tackling Woody Herbs

These Mediterranean staples require a different approach due to their tougher structure:

  • Strip leaves from woody stems (stems can be saved for stocks)
  • Use more aggressive pounding action initially
  • Salt is especially helpful for breaking down fibres
  • Consider briefly drying leaves before grinding for easier processing
  • Expect a coarser final texture than with tender herbs

Creating Classic Herb Preparations

Authentic Genovese Pesto

The mortar and pestle is the traditional—and superior—method for making true pesto:

  1. Crush 1 clove garlic with coarse salt until smooth
  2. Add 30g pine nuts and grind to a paste
  3. Add 60g fresh basil leaves in batches, pressing and twisting
  4. Incorporate 50g grated Parmigiano-Reggiano
  5. Slowly drizzle in 100ml extra virgin olive oil while continuing to grind
  6. Adjust salt to taste

Chimichurri Base

This Argentinian herb sauce benefits from mortar preparation:

  1. Grind garlic cloves with salt until smooth
  2. Add fresh oregano leaves and grind
  3. Add flat-leaf parsley in batches
  4. Transfer to a bowl and stir in olive oil, vinegar, and red pepper flakes

💡 Pro Tip

Chimichurri benefits from some texture, so don't over-grind. Stop when the herbs are bruised and broken but not completely smooth.

Thai Green Curry Paste Foundation

Start your curry paste with the aromatic trinity:

  1. Pound coriander roots with white peppercorns until broken
  2. Add garlic cloves and pound until smooth
  3. This foundation can then receive green chillies, lemongrass, galangal, and other paste ingredients

Advanced Tips for Better Results

Temperature Matters

  • Chill your mortar in the refrigerator before grinding to help preserve volatile compounds
  • Cold herbs hold their oils better than room-temperature ones
  • In hot weather, work in short bursts to prevent heat buildup from friction

Building Flavour Layers

The order in which you add ingredients affects the final result:

  • Always start with the hardest ingredients (garlic, ginger, tough spices)
  • Add medium-textured items next (nuts, woody herb stems)
  • Finish with delicate leaves and liquids

Preventing Oxidation

  • Work quickly once leaves are bruised
  • Adding oil early creates a protective barrier
  • A small amount of acid (lemon juice, vinegar) can slow browning
  • Blanching herbs briefly in boiling water and shocking in ice water before grinding helps maintain colour for some applications

✅ Quick Reference

Tender herbs: Gentle pressing, work quickly
Woody herbs: Aggressive pounding, use salt
All herbs: Small batches, proper order, minimal heat exposure

Storing Ground Herb Preparations

Freshly ground herbs are best used immediately, but you can extend their life:

  • Cover pesto and similar preparations with a thin layer of olive oil to prevent air contact
  • Store in airtight containers in the refrigerator for up to one week
  • Freeze in ice cube trays for longer storage (up to 3 months)
  • Accept that colour will darken over time—the flavour remains excellent

Conclusion

Grinding fresh herbs with a mortar and pestle is one of the most rewarding kitchen skills you can develop. The immediate release of aromatics, the control over texture, and the connection to centuries of culinary tradition make this technique invaluable for any serious cook. Start with simple preparations like herb pastes and salts, then progress to more complex recipes as your technique improves. Your cooking will be transformed by the depth of flavour that only properly ground fresh herbs can provide.