Step 1Drain peas and combine in small saucepan with water and 1 teaspoon salt. Bring to simmer and cook until just tender, 15 to 20 minutes.
Step 2Melt butter in nonstick skillet over high heat. When butter has foamed and foam has receded, add mushrooms. Cook, stirring occasionally, until mushrooms begin to brown, about 5 minutes. Add garlic and cook, stirring, until very fragrant, 2 to 3 minutes.
Step 3When peas are done, drain and add to mushrooms. Stir together and season to taste with salt. Add healthy grind of pepper. Add parsley and stir well, then add lemon juice. Taste and adjust seasoning; mixture may need a little more lemon juice.