Sort lentils and discard debris. Rinse lentils, drain, and put in a 2- to 3-quart pan. Add broth and 1 teaspoon garam masala. Bring to a boil over high heat. Stir, and when boil resumes, reduce heat to a gentle simmer; stir occasionally, until lentils are barely tender to bite, about 5 minutes. Pour into a strainer over a bowl and drain well; reserve broth for other uses or discard. Mix 1 1/2 teaspoons garam masala with lentils.
Rub 2 baking pans (each 10 by 15 in.) evenly with oil. Divide lentils equally between pans and spread into a level layer.
Bake in a 375° regular or convection oven until lentils are lightly toasted and crisp to bite, 10 to 12 minutes, stirring occasionally. Let cool in pan about 10 minutes. Lentils may soften when cool; if so, return to oven and stir occasionally until they are again crisp to bite.
Pour lentils into a serving bowl. Add more garam masala and salt to taste. Serve, or store airtight up to 2 weeks.
Nutritional analysis per tablespoon.